Outbreak Report
Outbreak of Salmonella Agona phage
type 40 associated with the Street Spice
Festival, Newcastle upon Tyne
February / March 2013
ILOG 8168
Report date: 19 June 2013
Report prepared by: Dr Kirsty Foster, Consultant in Health Protection on behalf of the
Outbreak Control Team
This is the outbreak report of an investigation which was carried out by the former Health
Protection Agency and its partner organisations.
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© Crown Copyright 2013
Published June 2013
2
Contents
Section
Page
1
Executive Summary
5
2
Background
7
3
Coordination of the response
7
4
Investigations
11
5
Results
14
6
Control measures
24
7
Legal issues
25
8
Communications
26
9
Hypothesis
28
10
Conclusion and discussion
28
11
Recommendations
31
12
Actions taken as a result of this investigation
33
Appendices
1–3
Analytical Studies: methods and results
4
Food and Environmental sampling results
5
Communications materials
3
Acknowledgements
This was a very large outbreak, which developed rapidly over a short time period; I
would like to thank all members of the outbreak control team for their hard work on
this complex investigation, in particular the staff of the environmental health team
who worked tirelessly over the first week of the investigation to contact the hundreds
of people reporting illness and gather all necessary information. Thanks also go to
the laboratory staff for the rapid processing of the large number of specimens.
Dr Kirsty Foster, Chair of the Outbreak Control Team
Abbreviations and glossary
CHP
Consultant in Health Protection
EHO
Environmental Health Officer
FWE
Food Water and Environment
GBRU
Gastrointestinal Bacteria Reference Unit
GP
General Practitioner
HPA
Health Protection Agency
HPU
Health Protection Unit
ILOG
A reference number used to coordinate the collation of
microbiological results from the different laboratories, any
microbiological specimen that was suspected to be
connected to this outbreak, was given the same ILOG
reference number (8168)
NCC
Newcastle City Council
OCT
Outbreak Control Team
PCR
polymerase chain reaction
PCT
Primary Care Trust
PFGE
Pulsed-field gel electrophoresis
PT 40
phage type 40
sp.
Species
4
1. Executive Summary
1.1. Background
This report describes the investigation of a large outbreak of gastro-intestinal
illness in people who attended the Street Spice Festival held in Newcastle
between 28 February and 2 March 2013.
1.2. Coordination of response
The outbreak investigation was coordinated through a multi-agency outbreak
control team (OCT), chaired by a consultant in Health Protection from the
North East Health Protection Unit, with representatives from Newcastle City
Council (Environmental Health / Public Protection and Public Health), NHS
North of Tyne, the laboratory services of the Health Protection Agency
(Newcastle Laboratory, the Food, Water and Environmental Laboratory at
York and Gastrointestinal Bacterial Reference Unit, Colindale) and specialist
epidemiology teams from the North East Regional Epidemiology Unit and
HPA Colindale.
1.3. Investigation
Investigation of human cases of illness was carried out by the Environmental
Health team of Newcastle City Council, working closely with the Health
Protection Unit.
The investigation of food preparation and source of ingredients was led by
the Environmental Health team and involved liaison with environmental
health teams in other local authorities involved in the food chain and with the
Food Standards Agency.
The Health Protection Unit coordinated the on-going communication with
cases; communication to the public was jointly coordinated by
communications teams from Newcastle City Council and the HPA, with
Newcastle City Council acting as the first point of contact for media enquiries.
Analytical studies (a cohort study of people who attended the event, a followup study of cases and a capture-recapture study to estimate the total number
of cases) were undertaken by the Regional Epidemiology team of HPA North
East.
1.4. Results
413 people reported illness to the city council following the event. Cases had
attended the event on any of the three days of the festival suggesting an ongoing source of infection during the whole event.
29 cases of Salmonella were confirmed from people reporting illness; 25 of
these cases were a newly identified strain of Salmonella, Salmonella Agona
phage type 40. Other cases were Salmonella Hadar (1), Salmonella Cero (1),
Salmonella Typhimurium (1) and an untyped Salmonella (1).
5
Further investigations using a Polymerase Chain Reaction (PCR) assay
suggested that a number of other faecal organisms, including
enteroaggregative Escherichia coli and Shigella, may have contributed to the
burden of illness.
Salmonella Agona phage type 40 was isolated from curry leaves (samples
from the same batch of leaves used at the event).
Pulsed-field gel electrophoresis (PFGE) confirmed that the S.Agona isolates
from human and food specimens were indistinguishable.
The epidemiological findings from a cohort study supported the
environmental and microbiological findings. In total 827 people responded to
the survey of which 306 were classified as cases. Risk factors associated
with illness included eating from one section of a particular stall and eating a
food item containing uncooked curry leaves.
1.5. Conclusions
This was a large outbreak of gastro-intestinal illness, with Salmonella Agona
PT 40 confirmed in 25 cases and also isolated from a food ingredient used at
the event.
Findings from further laboratory analysis suggest that other faecal organisms,
including entero-aggregative Escherichia coli and Shigella, may also have
contributed to the burden of illness.
The OCT concluded that the use of uncooked curry leaves, which were
contaminated with Salmonella Agona PT40, was the mechanism of
transmission of infection.
After consideration of the findings of the investigation, Newcastle City Council
decided not to take formal action in this case. This decision, based on the
council‟s enforcement policy, took into account the lack of clear, official
advice about the use of curry leaves and the overall good standards of food
hygiene at the festival.
6
2. Background
The Street Spice Festival (a charity event) was held in Times Square, Newcastle
upon Tyne between 28 February (Thursday) and 2 March (Saturday) 2013. The
event had been well publicised in local print and social media and drew visitors
from across the North East.
3. Coordination of response
3.1. How the incident came to light
The organiser of the event contacted the Environmental Health (EH)
department at Newcastle City Council (NCC) first thing on Monday 4 March
following reports of illness made to him (directly and via Twitter and other
social media sites) over the weekend.
People also contacted the EH department directly on Monday 4 March.
The EH team contacted the North East Health Protection Unit (NEHPU) on 4
March; on the first day the number of reports of illness was in single figures
and it was agreed to collect as much information as possible from those
parties. However as numbers increased during the day, it was agreed that an
outbreak control meeting was required and this was arranged for 6 March.
The EH team continued to collect information and stool samples from
affected visitors to the event and to make contact with the event organiser
ready to inform the risk assessment discussion at the OCT meeting.
3.2. Setting
The event was held in a large marquee (40 x 15 m) in Times Square in
central Newcastle upon Tyne and was attended by 10 – 12,000 people over
the three days.
There were 18 hot food stalls and seven cold food / drink stalls and produce
traders present serving a variety of foods; most of the stalls were present for
all three days and most were from food premises within the North East of
England
The event was organised by the owners of Sachins restaurant, Newcastle
upon Tyne.
The event ran for the following times:
Thursday 28 February:
2 – 10pm (although 2 – 4pm was VIP only)
Friday 1 March:
4 – 10pm
Saturday 2 March:
12 – 10pm
7
3.3. Outbreak Control Team
A multi-agency outbreak control team (OCT) was convened with the following
members.
Name
Organisation
Dr Kirsty Foster (Chair) (x)
Jon Lawler (x)
Emma Thody (x)
Karen Lloyd (x)
Dr Russell Gorton
North East Health Protection Unit
North East Health Protection Unit
Health Protection Agency, North East
Health Protection Agency, North East
Regional Epidemiology Unit, HPA
North East
Regional Epidemiology Unit, HPA
North East
Regional Epidemiology Unit, HPA
North East
Regulatory Services and Public
Protection Division, Newcastle City
Council
Regulatory Services and Public
Protection Division, Newcastle City
Council
Regulatory Services and Public
Protection Division, Newcastle City
Council
Regulatory Services and Public
Protection Division, Newcastle City
Council
Regulatory Services and Public
Protection Division, Newcastle City
Council
Press Office, Newcastle City Council
Press Office, Newcastle City Council
HPA Food, Water and Environment
laboratory (York)
HPA Food, Water and Environment
laboratory (York)
Newcastle upon Tyne Hospitals Trust
Newcastle upon Tyne Hospitals Trust
Health Protection Agency laboratory,
Newcastle
Gastrointestinal Bacteria Reference
Unit, HPA Colindale
Gastrointestinal Bacteria Reference
Unit, HPA Colindale
Gastrointestinal, Enteric and
Zoonotic Department, HPA Colindale
Dr Alison Waldram
Daniel Gardiner
Stephen Savage
Vivienne Air (x)
Paula Davis (x)
Tracy Sweet
Colette Cassely
Nigel Whitefield (x)
James Plater (x)
Dr John Piggott
John Harford
Jennifer Collins
Michelle Payne
Dr Brendan Payne
Dr Kathie Grant
Dr Elizabeth de Pinna
Dr Chris Lane
8
Dr Tansy Peters
Gastrointestinal Bacteria Reference
Unit, HPA Colindale
Dr Derren Ready
Public Health Laboratory London,
Barts Health NHS Trust
Dr Fu-Meng Khaw (x)
NHS North of Tyne / Newcastle City
Council
Dr Dawn Scott
NHS North of Tyne / Newcastle City
Council
Helen Robinson
NHS North of Tyne / Newcastle City
Council
Lynda Seery
NHS North of Tyne / Newcastle City
Council
(x) Indicates people who were also members of the communications planning
subgroup
The group met a total of seven times (in face to face meetings and by
teleconference) between 6 March and 12 April.
A communication planning subgroup also met on two occasions to agree specific
issues relating to communication with people reporting illness / release of
preliminary investigation findings.
3.4. Chronology of events: February – May 2013
Date
28 February – 2
March 2013
4 March
5 March
6 March
8 March
8 March
Event / action
Street Spice Festival held in Newcastle upon Tyne
Reports of illness from event organiser and members of public
who attended the festival made to Newcastle City Council
Environmental Health team.
Initial discussion and risk assessment between NCC EH team
and North East Health Protection Unit.
Agreed to convene multi-agency Outbreak Control Team (OCT).
Number reporting illness = ~20
NCC EH team visit Sachins restaurant to gather information
and food samples
First OCT meeting
Number reporting illness = 65
Initial food histories seemed to identify a particular stall and food
type.
EHOs continuing to interview new cases and to investigate food
preparation at stalls attending the event.
Information sent to GPs and laboratories across the region to
enable further case-finding
NCC alerted Food Standards Agency (FSA) about outbreak
Second OCT meeting
Number reporting illness = 250
4 confirmed cases of Salmonella (O4, g)
9
8 March
Web-based cohort study launched (for all attendees ill and not ill)
11 March
Third OCT meeting
Number reporting illness = 382
14 confirmed cases of Salmonella
13 March
Preliminary results from analytical study show association
between illness and food from Sachins stall and with the South
Indian food items
Fourth OCT meeting
Number reporting illness = >400
20 cases of confirmed Salmonella
Presumptive typing from Colindale – Salmonella Agona
Salmonella O4, g isolated from curry leaves used in coconut
chutney
Findings of food samples reported to FSA by NCC and HPA
14 March
15 March
19 March
19 March
20 March
20 / 21 March
27 March
28 March
12 April
Analytical study analysis showed shows strongest association
between illness with coconut chutney
NCC submitted incident report to FSA
First separate Communications planning sub-group meeting
Actions regarding communication to people reporting illness
Fifth OCT meeting
Numbers reporting illness = >400
28 confirmed cases of Salmonella
Further typed specimens identified as new strain of Salmonella
Agona phage type (PT) 40
Alert sent to European Centre for Disease Control (ECDC)
Epidemic Intelligence Information System (EPIS)
Second Communications planning group meeting
Update on investigation sent to all people who had reported
illness to EH department or reported illness via the on-line
survey.
Sixth OCT meeting
Numbers reporting illness = 413
29 confirmed Salmonella cases
Case follow-up survey launched
Seventh OCT meeting
Number reporting illness = 413
29 confirmed cases of Salmonella
Of which 25 cases Salmonella Agona PT40
Further isolates from curry leaves identified as Salmonella Agona
Outbreak investigation closed.
NCC work on possible enforcement action continues.
10
29 April
10 May
Case follow-up survey closed
Further follow-up of cases with continuing illness
4. Investigations
4.1. Epidemiological
4.1.1.
Case definitions used
The OCT agreed the following case definitions:
Confirmed case: A person with laboratory confirmed Salmonella (O4g)
who attended the Street Spice event between 28 February and 2 March
Probable case: A person who reports diarrhoea + two other symptoms
from abdominal pain / cramps, nausea, vomiting, fever starting after
attendance at the Street Spice Festival between 28 February and 2
March.
During the investigation, these case definitions were refined as further
information about cases and symptoms was gathered.
Final case definition: A person with diarrhoea who became ill between 12
hours and 5 days after attending the Street Spice event.
4.1.2.
Case finding
Initially people self-reported illness to NCC EH department; these tended
to be groups of friends or families.
A smaller number of cases of illness were reported to the HPU by several
routes, including self-report, GP report or following routine investigation
of a Salmonella case. NCC EH department were provided with details of
all these cases.
On 6 March 2013, a letter was sent to GPs asking them to notify any
cases of illness reporting attendance at Street Spice Festival (and collect
a specimen under ILOG number).
As awareness of the outbreak spread, consultant microbiologists at local
NHS laboratories were asked to alert the HPU of any positive Salmonella
results where clinical details on the specimen mentioned “Street Spice”.
Information was also shared between attendees on social media sites
(Twitter and Facebook) advising people to contact EH department; in
some cases this occurred before the formal communication from the
OCT.
4.1.3.
Exposures
Staff from the NCC EH team collected food histories / exposures from
people reporting illness. After the initial 20 – 30 cases, it became clear
that attendance at the Street Spice Festival was the common factor in
11
those reporting illness, so to make information collection / case
interviewing manageable the investigation focussed on attendance and
food eaten at the festival.
As described above, there were many stalls serving a range of foods;
details of stalls visited and foods eaten were collected and recorded.
4.1.4.
Analytical studies
At the first OCT meeting, the group agreed that a cohort study should be
undertaken; it was agreed to use a web-based study to capture the large
number of attendees and to publicise this through social media
(Facebook and Twitter) as well as regional television and print media.
During the course of the investigation, when it was apparent that cases
were reporting prolonged symptoms, the OCT agreed that a follow-up
study of cases should also be undertaken.
Of the 592 cases reported by any method, 527 were sent a link to the
case follow-up survey by email if available, otherwise by post.
Details of the survey were circulated on 28 March, with a closing date for
responses of 22 April.
Cases who reported on-going illness in the case follow-up study were recontacted on 10 May to determine the final length of symptoms / end of
illness.
As there were different sources of information on case numbers, a
capture-recapture analysis was also undertaken to estimate the true
number of people affected.
See Appendices 1-3 for more detailed description of the methodology
used in the analytical studies
4.1.5.
Data management
Case details were recorded on a spreadsheet held by the NCC EH team.
Laboratory results were managed by the Health Protection Unit (HPU) as
results came from both the HPA Newcastle laboratory, based at
Newcastle upon Tyne Hopsitals, and other NHS laboratories across the
region.
The EH and HPU teams ensured that the two lists of cases (reported
illness and laboratory-confirmed infection) were reconciled and deduplicated, and that all appropriate investigations and follow-up were
undertaken.
4.2. Microbiological
4.2.1.
Sample collection
Initially members of the EH team at NCC collected faecal samples from
people reporting illness and transported the samples to the laboratory.
However, as the numbers of people reporting illness rapidly increased,
this arrangement became impractical and people were advised to submit
specimens via their GP; this advice was complemented by the alert to all
GPs in the region asking them to collect samples and submit them using
12
the outbreak ILOG number so that they would be processed at the HPA
laboratory and results easily collated.
4.2.2.
Laboratories used
Arrangements were made for specimens to be processed at the HPA
laboratory, Newcastle (Freeman Hospital) using the ILOG number to
identify the specimens as part of the outbreak.
In accordance with standard practice at HPA and NHS laboratories,
isolates from all positive cultures were sent to the Gastrointestinal
Bacteria Reference Unit at HPA Colindale for further typing.
4.2.3.
Microbiological testing
Samples were tested for standard bacterial pathogens (Salmonella,
Campylobacter, E coli O157, Shigella), Cryptosporidium, Norovirus,
Clostridium perfringens and Bacillus cereus.
As the information about likely organism and food source evolved and
negative results from certain tests were received, the testing panel was
reduced to bacterial pathogens only.
Because there were a relatively low number of confirmed Salmonella
infections on the early specimens analysed at the HPA laboratory, it was
agreed that specimens would be re-cultured on to alternative Salmonella
selective media along with a repeat Xylose lysine deoxycholate (XLD)
culture plate. (The alternative media were Brilliance Salmonella (Oxoid),
ASAP (a chromogenic Salmonella medium from AES); all repeat testing
of specimens were assessed both pre and post-enrichment culture).
Subsequent specimens were cultured on both media simultaneously.
A sub-set of faecal samples (positive and negative by culture) from the
HPA laboratory were sent to the Public Health Laboratory, London for
multiplex PCR testing for a range of gastro-intestinal bacterial pathogens.
4.3. Environmental
4.3.1.
Inspection
Environmental Health Officers from NCC contacted the organiser of the
event on 4 March and gathered information about the event and the
premises used.
On 5 March, they visited the kitchen at Sachins restaurant which is where
the implicated foods had been prepared.
4.3.2.
Food preparation
Staff from the EH team gathered detailed information on the foods
prepared at the implicated stall; information was gathered from the
restaurant staff involved in food preparation prior to the event and the
staff involved in cooking and serving foods at the stall.
Details of ingredients, exactly how they were handled, prepared and
served were gathered during the investigation.
13
4.3.3.
Food and environmental sampling
Samples of any remaining foods or ingredients which were used by the
implicated stall were collected.
Environmental samples, including swabs of food preparation and contact
surfaces, equipment and containers, were collected from the restaurant
kitchen. As the event had finished and the stalls had been dismantled by
the time illness was reported it was not possible to collect samples from
the areas where food was served to customers.
The EH team also visited the two local suppliers to collect samples of
additional ingredients. These were foods known to have been used in the
preparation of implicated dishes. As there were no foods from the same
batches as those used at the festival, samples from other batch codes
were taken for comparison.
Foods collected over several visits to the restaurant and suppliers were
coconut milk powder, desiccated coconut, asafoetida, whole green chilli,
fresh coriander, birdseye whole green chilli, fresh ginger, curry leaves*,
urad dall (black lentils), dried basmati rice, dried long grain rice, toor dall,
chilli powder, chicken tikka, cooked dhal, garam masala, cooked rice.
Environmental samples were collected from wash hand basin tap,
blender blade, onion basket, fridge handle, food containers, preparation
bench and a shelf above preperation bench.
All food and environmental samples were sent to the HPA Food, Water
and Environmental laboratory at York.
* the curry leaves were originally recorded as “dried” but it was confirmed
on later checking that fresh leaves had been used and sampled.
5. Results and interpretation
5.1. Epidemiological
The reporting of illness and identification of cases of confirmed infection
associated with this outbreak was complex. As described in the earlier
sections of the report, cases initially contacted the EH department at NCC to
report illness and these cases form the majority of cases included in this
report.
However, cases also came to light through a number of other sources
including direct reporting to the Health Protection Unit, through confirmed
Salmonella (O4,g) detected in local NHS laboratories not tested at the HPA
laboratory and through illness reported on the on-line cohort study.
Findings from all of these sources have been used in the descriptive
epidemiology of this outbreak.
5.2. Descriptive epidemiology
A total of 413 people reported illness (gastro-intestinal symptoms) to the NCC
14
EH department following attendance at the Street Spice Festival.
These reports of illness were either made directly to the department or were
made during follow-up of a positive Salmonella O4,g laboratory result.
Further cases of illness were received through the on-line survey of festival
attenders, making a total number reporting illness of 592.
From the entire dataset (EH list, laboratory list and illness reported on survey)
Table 1: People reporting illness following attendance at Street Spice Festival
Gender
Female
Male
Age group
N
<20
20-29
30-39
40-49
50+
Unknown
Total
% by
age
group
4.2
11
44 16.7
81 30.8
52 19.8
41 15.6
34 12.9
263 100.0
% by
gender
52.4
33.1
45.0
50.5
46.6
50.7
44.4
N
% by
age
group
3.2
10
88 28.3
93 29.9
49 15.8
45 14.5
8.4
26
311 100.0
Total
Unknown
% by
gender
47.6
66.2
51.7
47.6
51.1
38.8
52.5
N
% by
age
group
0.0
0
5.6
1
6 33.3
2 11.1
2 11.1
7 38.9
18 100.0
% by
gender
0.0
0.8
3.3
1.9
2.3
10.4
3.0
% by
age
group
% by
gender
21
3.5
133 22.5
180 30.4
103 17.4
88 14.9
67 11.3
592 100.0
100.0
100.0
100.0
100.0
100.0
100.0
100.0
N
5.2.1.
Period of exposure
The period of exposure was the three days of the festival – Thursday 28
February to Saturday 2 March 2013.
15
5.2.2.
Epidemic curve
Figure 1: Epidemic curve of onset set by “days after attendance" from the
cohort study
60
Number of cases
50
40
30
20
10
Day of
attendance
+1
+2
+3
+4
Symptoms
The symptoms described when people first reported illness were
predominantly diarrhoea and abdominal pain / cramp, with a smaller
number of reports of nausea and vomiting.
Table 2 shows symptoms and duration of illness for those fitting the case
definition, using data from the case follow-up study together with further
information from cases still reporting illness at the time of completion of
the follow-up study.
Fifty eight cases reported relapsing symptoms (resumption of diarrhoea
after a symptom-free period).
16
Evening
Afternoon
+5
5.2.3.
Incubation period
The mean incubation period (from case follow-up study) was 1.5 days
(range 1 – 4 days).
5.2.4.
Morning
Early morning
Evening
Afternoon
Morning
Early morning
Evening
Afternoon
Morning
Early morning
Evening
Afternoon
Morning
Early morning
Evening
Afternoon
Morning
Early morning
Evening
Afternoon
Morning
Early morning
0
Table 2: Symptoms and duration of illness from case follow-up study
Symptom
Diarrhoea
Number
Percentage
351
100
91
58
44
18
still ill
14
not still ill
337
Abdominal pain
320
still ill
11
not still ill
308
Nausea
Fever
Vomiting
203
155
64
Mean
duration
12.3
32.4
11.4
9.2
33.1
8.3
4.6
2.8
1.7
Median
duration
11
27
11
7
34
7
3
2
1
Duration
range
1-49*
25-49*
1-43
1-47*
14-47*
1-34
1-28
1-14
1-6
5.2.5.
Hospital admissions
Information about hospital admissions was difficult to verify with such a
large number of people affected; in the case follow-up study two people
reported hospital admission (0.5% hospitalisation rate), but these
admissions were short-lived. Another six people visited hospital with
symptoms but were not admitted.
5.2.6.
Foods eaten
The EH team identified that a wide range of foods were served across
the event, however from early on in the investigation, it was clear that a
particular stall and food items were reported in high numbers by people
who were ill.
The foods most frequently reported as eaten were the “South Indian”
foods served from the Dosa Hut section of the Sachins stall, and an
association between illness and consuming these foods was found in the
cohort study with no associations with food from other stalls.
Investigation of food preparation therefore concentrated on foods from
the Dosa Hut section of the Sachins stall. The food in the Dosa Hut
section was prepared by a guest chef invited to the event by the
organiser.
Approximately 900 – 1000 portions of these foods were served over the
three days of the festival.
5.2.7.
Food preparation including findings of inspection
The dishes served at the Dosa Hut section of the Sachins stall, which
were all vegetarian, were a dosa, an uttaphum and a vada.
Each dish was accompanied by coconut chutney and a lentil samba
sauce unless specifically requested not to by the customer.
17
Information was gathered about the preparation of the foods used at the
festival by taking statements from all of the chefs and kitchen porters who
worked in the kitchen at the time. They informed officers that the
preparation of these foods involved several stages:
A batter was made prior to the event in the restaurant kitchen for the
dosa and uttaphum; this involved soaking the dried lentils and rice
overnight at room temperature, the mixture was then blended the
following day to make the batter.
The dosa filling consisted of potato, onion, ginger, curry leaves and
spices which had been cooked at the restaurant, blast chilled and then
reheated on site and hot held.
The uttaphum topping which consisted of onions, peppers and coriander
was cooked to order on site.
The vada contained chickpeas, spinach and spices and was prepared,
deep fried, blast chilled in Sachins kitchen and was reheated to order on
site.
The samba consisted of lentils, onions, tomatoes and spices which were
slow cooked then blast chilled in Sachins kitchen. Then reheated on site
and then hot held.
The coconut chutney was made by liquidising together desiccated
coconut, coconut milk, ginger, chilli, fresh curry leaves, coriander, salt,
green chillies and water.
The curry leaves were purchased locally and were stripped from the
stalks by two members of the restaurant staff on 27 February; up to 7
bags of curry leaves were prepared in this way. Leaves were then put all
together in a larger plastic bag, placed in the chiller, to be used by the
chef in preparation of the chutney (see section 6 for more detail on food
chain supply of curry leaves).
Batches of chutney were made on each day of the event.
The leaves were taken out of the larger bag and washed by the chef
during the preparation of the chutney by holding them under cold running
water. They were then added into the chutney mixture whole and ground
up using a stick blender.
The leaves were not in contact with any other surfaces in the kitchen
during this preparation and a designated area of the kitchen was used.
Once made the chutney was stored in containers which were covered
and stored in the fridge at Sachins kitchen before being transported to
the festival site.
A large fridge was available at the site which was used for the storage of
chutney. A quantity of chutney was kept in a small serving bowl on the
18
stall.
5.2.8.
Analytical studies
(see Appendices 1 - 3 for further details of all analytical studies)
5.2.8.1. Cohort study.
The study was undertaken using a web-based questionnaire.
Attendees at the Street Spice Festival were invited to respond to
messages distributed via Twitter, a Facebook group and released in
a press statement.
827 completed responses were received; of these, 347 reported
gastro-intestinal symptoms following the event and 306 met the case
definition for the analytical study.
Univariate analysis found significant association between illness and
eating food from the Sachins stall (Risk Ratio (RR) = 8.59, 95% CI
6.08 – 12.14) and eating the South Indian foods (RR = 7.77, 95% CI
6.10 – 9.91). 89% of the cases reported eating South Indian foods.
There were no associations between being ill and any of the other
stalls.
Looking at specific food items served at the Sachins stall, there were
significant associations between illness and eating several food
items including coconut chutney (RR = 4.39, 95% CI 3.73 – 5.17),
dosa (RR = 4.29, 95% CI 3.62 – 5.08), uttaphum (RR = 2.73, 95%
CI 2.40 – 3.11) and vada (RR = 2.65, 95% CI 2.30 – 3.05).
On stratified analyses, associations with the standard restaurant
foods (i.e. non-South Indian foods) were reduced (univariate RR
1.69, adjusted RR 1.23) suggesting that confounding between the
different foods had raised the univariate risk ratios. When individual
Sachins food items were stratified by coconut chutney the
associations were similarly reduced.
The findings of the cohort study are that consuming South Indian
foods from the Dosa Hut section of the Sachins stall was statistically
significantly associated with illness and explained 89% of the cases.
This is very strongly suggestive that this association was causal.
The strongest association with a single food item was with coconut
chutney, which was served as a side dish rather than as a menu
item in itself and as such is likely to have not been reported as an
exposure by all people consuming it. This is the most likely
explanation for the RR for coconut chutney being lower than for
South Indian foods as a whole, and for some other foods remaining
significantly associated with illness after stratification by reported
coconut chutney consumption.
However another possible reason for this is cross contamination
19
between the items, such that some portions of other foods became
contaminated and caused some of the illnesses. The study could not
distinguish between these possibilities, but nevertheless provides
strong evidence that the coconut chutney was the main vehicle of
infection.
Further details of the results of the cohort study are contained in
Appendix 1.
5.2.8.2. Case follow-up study
527 people who reported illness were contacted to complete the
case follow-up study, of which 374 responded (71% response rate);
351 respondents met the updated case definition (person with
diarrhoea who became ill between 12 hours and 5 days after
attending Street Spice) and were included in the analysis.
Symptoms and duration of illness are reported in section 5.2.4.
Of the 351 cases who completed the survey:
64.7% contacted some form of healthcare service because of their
symptoms; most commonly this was their GP (40%).
The cases that attended their GP visited between one and five times
(mean number of visits: 1.5).
Cases visited or contacted between one and five different healthcare
/ public health services.
35% reported that they had contacted the EH department at
Newcastle City Council about their illness.
59% had to take time off work due to their symptoms; the mean time
off work was 4.9 days (range 1 – 35 days), the total number of
working days lost was 995.
43% reported submitting a stool specimen. The mean number of
specimens submitted was 1.2, with a range of one to six samples.
Further details of the case follow-up study are contained in Appendix
2.
5.2.8.3. Capture-recapture analysis
Using the three sources of information about cases (people reporting
illness to EH department, laboratory results of people not known to
the EH department and people reporting illness via the on-line
survey for the cohort study) a capture-recapture analysis was
undertaken to estimate the true size of the outbreak.
The estimated total number of people ill was 926 (95% CI: 628 –
20
1224). The upper limit of the confidence intervals exceeded the total
number of servings of the suspected food. This may reflect the
imprecision of the estimate and resulting wide confidence intervals,
though inaccuracies in the reported number of servings, sharing of
single portions between customers and cross contamination might
all be reasons that more people could be ill than reported portions
served.
Further details of the capture-recapture study are contained in
Appendix 3.
5.3. Microbiological / laboratory results
5.3.1.
Human isolates
5.3.1.1. Microbiological culture and phage typing
110 faecal specimens were submitted to the HPA laboratory,
Newcastle under the ILOG outbreak number.
29 samples were positive on culture for Salmonella.
Of these, 25 were Salmonella Agona phage type 40.
There was 1 case of Salmonella Cero, 1 case of Salmonella Hadar,
1 case of Salmonella Typhimurium and 1 Salmonella sp. which was
untyped.
21 of the confirmed Salmonella cases were identified at the
Newcastle HPA laboratory, and 8 at a number of local NHS
laboratories in the North East region.
It is not possible to say how many specimens were submitted to
other laboratories, but the case follow-up study suggested that at
least 151 people submitted specimens.
5.3.1.2. PCR testing
Molecular (PCR) testing identifies genetic material from microorganisms; by selecting DNA fragments with specific characteristics
of organisms, PCR testing can be used for rapid identification of
individual species in clinical specimens.
The assay used in this outbreak tested for Salmonella,
Campylobacter (coli and jejuni), verocytotoxigenic E. coli (VT toxin 1
and VT toxin 2), Shigella and Entero-aggregative E. coli.
The PCR multiplex assay is not a standard clinical diagnostic
technique and was used in this outbreak as an adjunct to standard
laboratory investigations in an attempt to explain the low number of
21
laboratory confirmed infections and clinical picture of prolonged and
severe symptoms in the early stages of the investigation.
Eighty eight faecal samples, where there was sufficient sample left
after standard laboratory investigations were completed at the HPA
laboratory Newcastle, were sent to the Public Health Laboratory,
Barts NHS Trust, London for PCR testing.
The samples submitted for PCR testing included some which had
been positive and some which had been negative for Salmonella by
standard culture methods at the HPA laboratory.
Results from the PCR testing were consistent with people having
been exposed to other faecal pathogens.
Entero-aggregative E. coli, an organism commonly associated with
travellers‟ diarrhoea was detected by PCR in 80% of the samples.
The symptoms of entero-aggregative E. coli infection can be
prolonged and include abdominal pain and diarrhoea, which would
have been consistent with the pattern of illness described by those
affected in this outbreak.
Shigella was detected by PCR in 39% of the samples submitted.
The symptoms of Shigella include diarrhoea, nausea, fever and
abdominal cramps.
These findings, although not from a standard clinical diagnostic test,
suggest that a range of faecal organisms contributed to the burden
of illness associated with this event, with the most likely source
being from a contaminated food item.
E. coli detected on food samples including the curry leaves was
identified by standard culture methods and it is not standard practice
to undertake further typing on E. coli identified in food specimens.
Whilst the culture used for food samples would have detected
entero-aggregative E. coli, it is not possible to state definitively that
this was present on the food items.
5.3.2.
Food and environmental
5.3.2.1. Environmental swabs
All environmental swabs from the restaurant kitchens were negative
for Salmonella.
5.3.2.2. Food samples / list of results
Isolates of Bacillus detected above 105 cfu/g on the Rajah Garam
Masala and Dahl and the Salmonella isolates from the curry leaves
were sent to the GBRU at HPA Colindale for further typing.
Salmonella O4, g, E. coli and Enterobacteriaceae were isolated from
22
the curry leaves obtained from the restaurant and known to have
been from the batch used in the coconut chutney.
Further typing of the Salmonella isolates, undertaken at the HPA
laboratory at Colindale, identified Salmonella Agona PT 40.
A second batch of curry leaves from the same local supplied tested
negative for Salmonella.
Other food samples (fresh ginger, chilli and coriander) had high
levels of Enterobacteriaceae.
See Appendix 4 for full table of food and environmental results.
5.3.3.
Pulsed-Field Gel Electrophoresis analysis of human and food
samples
Pulsed-field gel electrophoresis (PFGE) was carried out on a sample of
human S. Agona isolates and the S. Agona isolates from the curry
leaves. The profiles were analysed using BioNumerics software (version
6.10; Applied Maths, Sint-Martens-Latem, Belgium).
Figure 2: Pulsed-field gel electrophoresis
Representative pulsed-field gel electrophoresis profiles of Salmonella
Agona PT40 isolates from patient and curry leaf samples shows them to
be indistinguishable.
5.4. Summary of results
As outlined above, the complex investigation of this large outbreak found
strong evidence linking the consumption of a dish containing a contaminated
food ingredient with gastro-intestinal illness.
Microbiological findings of a newly identified strain of Salmonella (Salmonella
Agona phage type 40) in human samples and from the food samples (the
23
fresh curry leaves from the batch used in food served at the event) were
supported by very strong epidemiological evidence from a large cohort study
which identified coconut chutney made with the uncooked curry leaves as
having the strongest association with illness.
Further molecular (PCR) investigations, undertaken to explore why there was
such a large burden of illness with a relatively small number of confirmed
cases of Salmonella, found that 80% of samples tested were positive for
entero-aggregative E.coli and 39% were positive for Shigella, both organisms
associated with travellers‟ diarrhoea and whose clinical features match with
those described by many of the people reporting illness in this outbreak.
There is evidence from standard tests that E.coli was present on the leaves
in addition to Salmonella, but we were not able to test food samples from the
festival using molecular techniques and have no evidence as to whether or
not this was the entero-aggregative E.coli strain.
Although the PCR test is newly developed and is not fully validated for use as
a routine clinical diagnostic test, the findings from its use in this outbreak
suggest an explanation for the burden of illness experienced; that is that the
leaves may have been contaminated, and the reported illness caused, by
more than one organism.
6. Control measures
The OCT identified three areas of public health risk
An infected food handler
All staff involved in preparation and serving of the food at the South East Indian
food stall were interviewed and submitted faecal specimens.
There was no reported diarrhoeal illness in the staff and all faecal specimens
were negative for Salmonella.
A contaminated food item / ingredient, with potential for continuing presence in
the food chain
As described above, detailed information about the preparation of the food items
was collected by members of the EH team.
Following the identification of Salmonella on the curry leaves used in the coconut
chutney, further investigation and control measures were undertaken.
EHOs from Newcastle City Council identified that the Newcastle retailer, where
the leaves had been purchased, got his supplies from a wholesaler in Yorkshire.
Newcastle EHOs worked with EH colleagues in Yorkshire to further investigate
the supply chain of the curry leaves.
The importer of the curry leaves in London and the exporter (in Pakistan) were
contacted directly by NCC EHOs. The importer confirmed that the curry leaves
were received as a wrapped product in a cardboard box imported via Heathrow
and no further treatment or labelling was carried out. The exporter confirmed that
24
the Airway bill is used as a means of traceability. They consider the product to
be raw although it is not labelled to this effect. The product did not undergo any
microbiological testing but they did provide a microbiological test of water used to
wash the curry leaves in Pakistan.
NCC EHOs then liaised with Port Health at the port of entry to arrange for further
leaves to be collected at port of entry and to be sent to the FWE lab in London for
analysis to establish whether the contamination of curry leaves from this supplier
was an on-going problem / public health risk. Samples collected on 11 April 2013
were negative on culture for Salmonella.
At a local level, EHOs ensured that the use of raw curry leaves was not usual
practice in the restaurant where the foods for the festival had been prepared. No
on-going risk from the use of this ingredient, for example by cross contamination,
was identified in the restaurant. The OCT therefore concluded that there was not
an on-going local public health risk.
A food incident report was sent to the Food Standards Agency (FSA) with details
about the outbreak and in particular the likely source of the infection and details
of the importer of the curry leaves. A number of updates were given to the
incidents branch and to the regional FSA team as the investigation continued.
There was discussion between the OCT and the FSA about whether specific
advice about the use of curry leaves needed to be issued. The advice from the
FSA was that whilst specific advice did not exist regarding curry leaves, standard
practice regarding storage and washing leaves would be an option.
Given that this was generic food-handling advice that should already be available
to food business operators and the public, the OCT did not consider it necessary
to issue specific advice during the outbreak.
Secondary transmission of infection
Advice was given to cases about the need for careful attention to hand / personal
hygiene whilst they had diarrhoeal illness. Cases were also advised to stay off
work / college until 48 hours symptom-free.
The case follow-up survey asked about illness in household or other contacts
(after the case‟s onset), 17 household cases were reported.
There were also two cases that fell outside of the case definition, because the
date of onset was later than the maximum incubation period used. Reasons for
their illness could have been unreported or asymptomatic primary cases,
genuinely longer incubation period or unrelated illness.
7. Legal issues
The investigation focussed on the collection of evidence related to:
Regulation (EC) No 178/2002 Article 14 which states Food should not be
placed on the market if it is unsafe, (this includes contamination)
and
EC Regulation 852/2004 Article 5 which states Food business operators shall
put in place, implement and maintain a permanent procedure or procedures
based on the HACCP principles.
25
Evidence to support or refute a due diligence defence in accordance with the Food Safety Act
1980 was also considered.
After consideration of the findings of the investigation, NCC decided not to take
formal action in this case. This decision, based on the council‟s enforcement policy,
took into account the lack of clear, official advice about the use of curry leaves and
the overall good standards of food hygiene at the festival.
8. Communications (see Appendix 5).
8.1. To the public
8.1.1.
To people reporting illness
People who reported illness to the EH team at NCC or to the HPU were
given verbal advice about preventing transmission of illness and advised
to seek medical advice if their symptoms worsened.
During the course of the investigation, a number of people who submitted
samples had a “negative” stool specimen (i.e. culture did not detect
Salmonella or any other pathogen) but still had symptoms and met the
case definition used by the OCT. These people were provided with
information about the investigation and the interpretation of “negative”
results.
An update was sent to all people who had reported illness (by post and
email) on 21 and 22 March 2013 providing an update on the investigation
and findings.
As noted above, the OCT also carried out a follow-up study of people
who reported illness. Cases were contacted by email or letter to invite
their participation in the study.
Letters were also sent to the people whose stool specimens were
positive for E.coli and / or Shigella on PCR testing.
8.1.2.
To people who attended the event
Information about illness in people who attended the event was already
circulating on social media sites linked to the event before the formal
OCT investigation started.
The OCT explored the amount of social media followers for the various
sites and found:
- Street Spice Festival Twitter account had 1851 followers
- HPA Twitter account had 6498
- Newcastle City Council Twitter account had 17228 followers
- Street Spice Facebook group had 734 “likes”
- HPA Facebook group had 779 “likes”
The social media sites were used to publicise the OCT investigation and
to invite people who had attended the event to participate in the cohort
study. The sites were also used to direct people to the press statements
about the investigation and early findings which were posted on the
26
Newcastle City Council and HPA North East websites.
8.1.3.
To the wider public
Information about the outbreak and the OCT investigation was provided
in a series of proactive press releases and interviews on local news
programmes. The Director of Regulatory Services for Newcastle City
Council acted as the spokesperson for the OCT on broadcast interviews.
8.1.4.
Survey of attendees
As noted above, a cohort study was undertaken of people who attended
the event. The information, and the link to the study questionnaire, about
this study was included in early press statements (8 March) and was
posted on the Street Spice website and HPA and NCC twitter accounts;
the information was also re-tweeted by a number of participants.
8.1.5.
Press statements and media reporting
Newcastle City Council led the multi-agency communications response
on behalf of the OCT and acted as the main point of contact for press
enquiries.
A reactive media statement, prepared on the 6 March, was issued to the
BBC local news team.
Further press statements were issued on 7 March, 8 March, 11 March,
15 March and 21 March.
Request for information from solicitors known to be acting on behalf of
some of the cases, the press and the BBC were received.
Holding statements were issued while the investigations were on-going.
8.2. Professional updates
8.2.1.
Laboratories
When it became apparent that people who were ill following the event
were attending their GP and submitting stool samples via NHS labs, an
alert about the outbreak investigation was sent to all consultant
microbiologists on 7 March asking them to report any clinical samples
where “Street Spice” mentioned in the clinical details.
On 8 March 2013, an update was sent to the same group when further
typing information (Salmonella O4, g) was known asking them to refer
any locally detected cases to the HPU.
8.2.2.
General practitioners
An alert was sent to all General Practitioners in the North East on 6
March 2013 outlining the OCT investigation process and asking them to
collect stool samples from any patient reporting diarrhoeal illness
following attendance at the Street Spice festival. GPs were asked to use
the ILOG number on specimens so that samples could be transported to
and processed at the HPA laboratory, Newcastle.
8.2.3.
HPA / PHE
Briefings on the outbreak investigation were sent to appropriate teams /
27
directorates within the Health Protection Agency / Public Health England.
8.2.4.
European updates
In line with requirements1, a report on the outbreak investigation was sent
to the European Surveillance to enable any linked cases detected in
Europe to be considered.
There were no reports of illness associated with attendance at the
festival, and no further cases of S. Agona PT40 from European partner
agencies.
9. Hypothesis
The hypothesis of the OCT is that contaminated curry leaves, which were used
uncooked in a chutney, were the source of illness in people attending the Street
Spice Festival.
The hypothesis is supported by the epidemiological and microbiological findings
of this investigation from both human and food samples.
The composition of the chutney may have increased the chances of Salmonella
and other organisms surviving and causing illness as the fatty nature (desiccated
coconut and coconut milk) of the chutney would have provided an ideal growth
medium for Salmonellae introduced from the contaminated curry leaves. Batches
of the chutney were held in a chiller onsite but it is possible that the chutney
decanted into smaller containers for service may have been held for some time at
ambient temperature on the stall which could have increased the growth rate of
the bacteria.
10. Discussion and conclusions
The OCT concluded that this large outbreak of gastro-intestinal illness, with
cases of confirmed Salmonella Agona PT40, was caused by the use of uncooked
fresh curry leaves, which were contaminated with the same strain of Salmonella.
A review of outbreaks reported to the HPA‟s electronic Foodborne and nonfoodborne gastrointestinal Outbreak Surveillance System (eFOSS)2 found that
this has been one of the largest food-borne outbreaks in the UK since 1992, and
was the largest UK outbreak where herbs or spices had been identified as the
suspected source of infection.
1
All member States are requested to submit information on outbreaks of GI infections, particularly where
there may be potential for foreign cases or the food vehicle is considered a potential risk through import to
other EU States. This then allows other member states the opportunity to check whether or not they have
cases that could be attributed to the same vehicle (or event where travel is included). Whilst this is not
mandatory, the benefits of reporting such events allow for better epidemiology across Europe.
2
HPA electronic Foodborne and non-foodborne gastrointestinal Outbreak Surveillance System (eFOSS).
The Health Protection Agency has operated a system of surveillance for general outbreaks of infectious
intestinal disease (IID) in England and Wales since 1992, which includes foodborne and non-foodborne
gastrointestinal outbreaks.
28
The organism
The Salmonella genus is composed of two species; S. enterica and S. bongori .
Salmonella enterica, which is a leading cause of gastroenteritis, is subdivided into
hundreds of serovars. Salmonella Agona is one of the serovars of S. enterica. S.
Agona is a non-typhoidal Salmonella.
Infection with Salmonella bacteria can cause gastroenteritis (diarrhoea,
abdominal cramps, and fever), which is usually a self-limiting, uncomplicated
disease lasting three to seven days. However, Salmonella infection can be more
serious causing dehydration, blood-poisoning (septicaemia) and abscesses. The
elderly, very young or immunocompromised are more prone to serious illness or
complications. Salmonella infection is usually acquired by eating food, especially
undercooked poultry, meat or eggs. Ready-to-eat products such as sandwiches
or other products can become contaminated with Salmonella bacteria and cause
infection. Salmonellae can also be transmitted directly from person to person via
the faecal-oral route, from an infected person to a foodstuff or from an infected
animal to a person.
The symptoms reported by cases in this outbreak were unusual in that diarrhoea
and abdominal pain persisted for longer than is commonly associated with
Salmonella infection.
Although Salmonella Agona has been previously identified, the specific phage
type, Salmonella Agona PT40 has not been recognised before in either food or
human samples.
Findings from the molecular (PCR) testing of specimens suggest that other
gastro-intestinal pathogens, including entero-aggregative E. coli and Shigella,
may have contributed to the burden of illness in people who attended the event.
The vehicle of transmission
Dried and fresh herbs and spices are known to be potential sources of
Salmonella and other organisms, and have been reported in the scientific
literature as the source of infection in a number of outbreaks.
Sampling studies have identified contamination of curry leaves with different
strains of Salmonella, but the strain identified in this outbreak had not been
detected before.
The HPA carried out a food survey of fresh herbs in 2007, involving 3,760
specimens. Of these, 21 specimens were of Curry leaves, 2 of which were
positive for Salmonella (#1 – S.Newport + S.Virchow PT 8, #2 – S.Virchow PT
21). Of the 21 specimens, details of country of origin were available for 10, (India
8, Cyprus 1, UK 1), none were from Pakistan3.
It is possible that curry leaves were contaminated with other strains of Salmonella
as well as other faecal organisms. Salmonella Hadar and Salmonella Cero were
found in stool samples from people reporting illness and entero-aggregative E.
coli and Shigella were identified on molecular PCR testing of stool samples. It is
not possible to say conclusively whether or not illness in these cases was caused
by contaminated food from the event.
3
Elvis et al. Microbiological study of fresh herbs from retail premises uncovers an international outbreak of
Salmonella. International Journal of Food Microbiology 134 (2009) 83–88
29
Understanding the risk from fresh leaves and safe food preparation
Although well-documented in the scientific literature, it is unclear whether there is
widespread understanding among food handlers and the public regarding the
potential for contamination of herbs and spices with Salmonella and other
pathogenic organisms. Anecdotal information gathered by EHOs during their
investigation suggested that many of those who were unwell perceived
vegetarian food to be associated with a low risk of food borne illness and food
handlers did not consider use of raw curry leaves to be associated with significant
risk.
This outbreak highlighted areas of uncertainty around the use of uncooked fresh
curry leaves.
Are they a ready to eat product i.e. intended for direct consumption?
Fresh herbs are commonly used as a food ingredient in both the commercial and
domestic setting. The majority of fresh herbs can be consumed raw or added to
food after cooking depending on local culinary practices. Used in this way, herbs
are considered to be in a ready-to-eat state. Regulation (EC) No. 2073/2005 on
microbiological criteria for foodstuffs defines ready-to-eat food as “food intended
by the producer or manufacturer for direct human consumption without the need
for cooking or other processing effective to eliminate or reduce to an acceptable
level micro-organisms of concern”4.
This may be open to interpretation. Staff at the restaurant involved in this
outbreak usually add curry leaves to food that is further cooked, so that leaves
are not ingested in their raw form. At this event, different types of food, from
another region of India, were prepared and the leaves were used raw.
During the investigation, the OCT members tried to establish whether this was
considered “normal practice” when preparing the coconut chutney. Several
different recipes for coconut chutney were found and these included use of raw
leaves and the use of “tempered” leaves (where leaves are heated, sometimes in
a small amount of oil, in a frying pan for between few seconds to a minute), thus
making it difficult to establish whether the practice of using raw leaves is
“accepted practice” in this style of cooking.
How to make the use of leaves safe
The fresh curry leaves implicated in this outbreak were sold in bunches that were
packaged in unlabelled plastic bags without batch details or instructions for use.
Consequently, people purchasing these leaves may have been unsure whether
they were safe to use uncooked and whether they needed to be washed before
use. At the time of the outbreak, there was no published guidance from the UK
Food Standards Agency regarding the use of curry leaves and specifically
whether these should be regarded as a ready to eat product.
4
European Commission (EC), 2005a. Regulation (EC) No. 2073/2005 of 15 November
2005 on microbiological criteria for foodstuffs. Official Journal of the European
Union L338, 1–26
30
Research has described how some faecal organisms, including Salmonella,
entero-aggregative E. coli and Shigella, can become tightly adhered to leaves
and can survive for long periods of time5; this would support the findings from this
outbreak of Salmonella Agona PT40 on the leaves, suggesting contamination
prior to the leaves being packaged and transported to the UK. This also raises
questions about whether washing the leaves would effectively remove pathogens
from the raw product.
Several factors influence the risk of transmission of pathogens on leaves and, as
such, determine which control measures will be most effective.
Leaves can be contaminated pre- or post-harvest, and the ability to adhere to
leaves differs depending on the organism. As attachment or adherence are prerequisites for contamination and subsequent transmission of pathogens these
factors will also be important in assessing the risk to human health.
Experiments have demonstrated that although post-harvest decontamination
(with chlorinated solutions) reduced bacterial contamination, it did not completely
eradicate either natural microbial population or human pathogens.
Of note, Salmonella Agona is thought to be less adherent to leaves than other
serovars (Typhimurium, Enteritidis and Seftenberg).
EHOs at Newcastle are working with the importer and with their Home Authority
on improving the advice given to their customers on the use of curry leaves. The
importers are currently developing a label for the product which will include clear
instructions for use.
EHOs in Newcastle have also established that normal practice in the restaurant is
to cook curry leaves, and therefore there was not an ongoing public health risk in
this situation.
Use of molecular techniques in outbreak investigation
The use of molecular (PCR) methods in this outbreak investigation added to our
understanding of the burden of illness. Further use of these tests in outbreak
situations will help develop our understanding of the significance of findings and
how the new technologies can be used to support and refine outbreak
investigation and the clinical significance of a wider range of gastro-intestinal
pathogens.
11. Recommendations
The key recommendations from this outbreak investigation focus on the use of
uncooked ingredients in foods.
As the investigation has highlighted, despite there being a wealth of scientific
literature about the transmission of human pathogens on the leaves of herbs and
other leaves and their being advice on the Food Standards Agency website about
the safe use of herbs and spices, the risks associated with using raw curry leaves
do not appear to be recognised by food handlers.
5
Berger et al. Fresh fruit and vegetables as vehicles for the transmission of human pathogens. Environmental
Microbiology (2010) 12(9), 2385–2397
31
Furthermore, the members of the public appeared to consider vegetarian food
“low risk” in terms of being the cause of their food poisoning.
Therefore, our recommendations are:
-
Better guidance on the use of curry leaves (and other leaf herbs) should be
developed to ensure that the food handlers and the public understand the
potential risks and how to minimise them
-
The Food Labelling regulations 1996 require pre-packed food to be appropriately
labelled. Action should be taken to ensure that curry leaves (and other herbs) are
labelled and include instructions for use
-
There should be further research into how often curry leaves are contaminated
and if they are, advice developed on their use in cooking.
If curry leaves are rarely contaminated, we would conclude that this outbreak
occurred due to an unusual combination of circumstances
-
Prevention at source – more research into how the organism gets into / onto the
ingredient and ways of preventing it – recognising that post-harvest washing may
be too early, too late or the cause of contamination in the first place.
As stated in the paper by Berger6 et al, „A better understanding of plant,
microbiological, environmental, farm, processing and food handling factors that
interact with one another to determine whether contamination occurs, and
whether pathogens survive or proliferate will support the development of
evidence-based policies, procedures, and technologies aimed at improving the
safety of fresh produce’
-
Risk reduction during food preparation – research into the effectiveness of
washing leaves in removing organisms and any appropriate guidelines,
particularly with regards to leaves intended to be used in foods without cooking
(noting that the method and timing of contamination may impact on the
effectiveness of washing)
Some more general issues regarding food preparation and serving at large
catered events also arose in this outbreak and we recommend:
-
Further research into whether routine refrigeration of uncooked products may
have reduced bacterial load in the foods that were contaminated
-
Food handlers working at festivals or other large events should retain samples of
foods for a period after an event to analyse if necessary; although we recognise
there may be practical challenges to undertaking this
-
Festival organisers should maintain an updated list of participating vendors and
request menus and recipes. This would assist greatly in the early stages of
investigations and facilitate the early identification of any on-going risk factors.
6
Berger et al. Fresh fruit and vegetables as vehicles for the transmission of human pathogens. Environmental
Microbiology (2010) 12(9), 2385–2397
32
We consider this could be achieved in ways that do not pose a significant
administrative burden.
-
Research into the growth of pathogens in uncooked food dishes and ways to
prevent it
This outbreak was the first time that molecular (PCR) assay had been used on
such a large number of “outbreak” specimens. The findings were helpful in
suggesting a possible cause for the burden of illness, but further research on the
use of PCR assay in outbreak situations needs to be undertaken. In particular,
we recommend that:
-
Research is undertaken on general (asymptomatic) and GI-ill (people with
diarrhoeal and / or other GI symptoms) population to help interpret PCR results
-
There should be clear communication between the clinical and FW&E laboratory
to discuss the microbiological (including molecular) tests to ensure a co-ordinated
approach to testing human and food / environmental specimens
-
A proposal for a survey of the microbiological quality of curry leaves (and other
leaf herbs) intended to be used in foods without cooking should be added to the
consultation for the UK Coordinated Study Liaison Group Programme 2014-15
The outbreak also highlighted the issue of “mixed pathogen” contamination as the
cause of gastro-intestinal illness. We recommend:
-
Awareness-raising amongst health protection and microbiological
professionals of this issue, including approaches to investigation which
identify all possible pathogens.
12. Actions taken as a result of this investigation
Recommendation
Better guidance on use of
curry leaves for food
handlers and the public
Ensure that pre-packed
curry leaves (and other
herbs) are labelled and
include instructions for use
Action taken
 A copy of this report has been
forwarded to the FSA with a
request that they consider our
findings and report back on how
advice might be developed
 The issue of contaminated leaves
will be presented to the Advisory
Committee on Microbiological
Safety of Food
 Discussion with Home Authority
with responsibility for the importer
of the curry leaves about improving
the information on the label on the
packaging of the curry leaves
By whom
PHE and
NCC
NCC
33
Research into
contamination of curry
leaves


Discussion with the scientific
branch of the FSA (plus copy of
the report) with a request that
further sampling of imported curry
leaves be considered
Proposal for survey of curry leaves
to be considered by the UK
Coordinated Study Liaison Group
PHE and
NCC
Prevention of
contamination at source

Issue raised with FSA
NCC and
PHE
Research into effect of
refrigeration on bacterial
load in contaminated food
Retention of food samples
from large catered events
Retaining lists of caterers
and menus at large
catered events
Research into growth of
contaminants in uncooked
food dishes
Use of molecular
technologies in outbreak
investigation / use of
molecular testing in
human and food samples
and interpretation of
results
Awareness of “mixed
pathogen” contamination
as a cause of outbreaks

Issue raised with FSA
NCC and
PHE

To be considered by FSA / LA
FSA / LA

To be considered by LA / FSA
LA / FSA

To be considered by FSA / LA
FSA / LA

A paper reporting the lessons
identified in this outbreak
investigation is being presented to
the PHE GI Programme Board –
for consideration of pilot project of
use of PCR in all outbreaks
PHE

Presentation of findings and
investigation techniques through
PHE professional networks
As above re molecular techniques
in outbreak investigation
Peer-reviewed publication
Conference presentations
ACMSF report
EPIS update
CIEH network and journal
PHE

Disseminate the findings
of outbreak investigation
to professional audiences
in UK and further afield





PHE and
NCC
34
Appendix 1 – Cohort Study (survey 1)
Aim
To investigate the association between exposure to foods served at the festival with illness.
Methods
A cohort study was undertaken in order to investigate the association between exposure to foods
served at the festival with illness. As the Street Spice Festival was a free to attend event with an
estimate of approximately 12,000 attendees over the three days, no list of attendees was
available. Accordingly invitations to participate in the survey were posted as links on the Street
Spice twitter and Facebook accounts, re-tweeted by the Newcastle City Council, the HPA and also
by a number of participants, and through hard copy press releases. The press releases were
reproduced in local and regional newspapers and reported on regional television. Initial invitations
were posted and released on Friday 8 March and repeat messages were issued over the course
of the next week. In addition those who had completed the survey were asked to encourage other
attenders within their household to participate, and to forward the invitations to any others that
they were aware had attended.
The invitations requested that all attendees at the festival complete an online questionnaire.
Those posted onto websites contained a clickable link to the survey. Hard copy releases
contained a short link to the survey created using Tinyurl!TM. The questionnaire requested
information on demographics, attendance, gastrointestinal illness, vendors visited and food items
consumed. Based on analysis of the initial information collated by Environmental Health it was
decided to include questions on the consumption of any food from all vendors, and detailed
information on food items eaten from three of the vendors, being the vendors which cases most
frequently reported having consumed food from. These were Sachins, The Rib Man and Monsieur
Crepe. Foods from Sachins were subdivided into „standard‟ menu items from the regular Sachins
menu, and „South Indian‟ foods which were prepared by a chef who had been specially invited to
the event and served from a separate part of the stall.
The questionnaire created using SelectSurvey, an application hosted and maintained by the
Health Protection Agency (HPA), and held on the secure SelectSurvey.NET network. The survey
was opened on Friday 8 March at 12 midday and closed on Monday 18 March at 10am. Figure 1
shows a timeline for the study together with dates of twitter/FaceBook messages and press
releases containing links.
Data from the survey was downloaded and analysed using STATA 12 (StataCorp). Responses
were used only if complete; completeness was defined as containing answers to all demographic,
attendance, illness and exposure questions. Responses were examined for duplicates; no
duplicates of completed questionnaires were found. Analyses included descriptive epidemiology;
univariate analysis of the association between exposure variables and illness by vendor, food
item, day and time visited, using risk ratio (RR) as the effect measure; stratified analysis using the
main risk factors to examine the effect of effect modification and confounding and a multivariable
analysis was completed using a logistic regression model. Statistical significance of relative risks
was inferred using 95% confidence intervals were calculated, along with p-values using Fisher‟s
exact test.
Interim results were presented to the OCT at meetings from the 11 March onwards.
Figure 1: Timeline of events and number of responses
Complete responses
Event times
Press publishing link
HPU notified
Twitter publishing link
OCT
500
450
Number of responses
400
350
300
250
200
150
100
0
AM
PM
AM
PM
AM
PM
AM
PM
AM
PM
AM
PM
AM
PM
AM
PM
AM
PM
AM
PM
AM
PM
AM
PM
AM
PM
AM
PM
AM
PM
AM
PM
AM
PM
AM
PM
AM
PM
50
28
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
Thu
Fri
Sat
Sun
Mon
Tue
Wed
Thu
Fri
Sat
Sun
Mon
Tue
Wed
Thu
Fri
Sat
Sun
Mon
Results
In total 1,309 responses to the survey were received, of which 827 were complete; 353 (42.7%)
males and 474 (57.3%) females. This equates to approximately 7% of the estimated 12,000
attenders; an estimate of the male:female ratio of attenders was not available. The number of
attendees who became aware of the survey cannot be estimated. The age-sex distribution is
shown in table 1; the distribution of cases is similar to that found in cases reported to
Environmental Health.
Cases were defined as anyone attending the Street Spice Food Festival that experienced
diarrhoea with onset between 12 hours and 5 days after attending. Of the 827 responders 306
(37%) met this definition; a further 41 reported other gastrointestinal symptoms. The median
incubation period was 1 day; the epidemic curve is shown in the main report as Figure 1.
Symptomatology is discussed in further detail in Appendix 2 (case follow up survey).
Cases occurred in people attending the festival on each of the days. The proportion of survey
responders who were ill was 35% of those attending on any day, and by individual day (1 to 3)
was 33%, 32% and 44% respectively. The proportion ill on day 3 was significantly higher than that
on the first two days (P<0.0001). No consistent trends were found with time of attendance, and
there was no association of length of attendance with illness.
36
Table 1: Respondents by Age, Sex and Case Status
Gender
Age
group
Cases
<20
20-29
30-39
40-49
50+
Unknown
Total
Non-cases
<20
20-29
30-39
40-49
50+
Unknown
Total
Male
Total
Female
N
% by
agegroup
% by
gender
N
% by
agegroup
% by
gender
N
% by
agegroup
% by
gender
2
29
45
29
21
1
127
1.6
22.8
35.4
22.8
16.5
0.8
100.0
20.0
35.4
41.3
52.7
42.9
100.0
41.5
8
53
64
26
28
0
179
4.5
29.6
35.8
14.5
15.6
0.0
100.0
80.0
64.6
58.7
47.3
57.1
0.0
58.5
10
82
109
55
49
1
306
3.3
26.8
35.6
18.0
16.0
0.3
100.0
100.0
100.0
100.0
100.0
100.0
100.0
100.0
5
51
89
45
34
2
226
2.2
22.6
39.4
19.9
15.0
0.9
100.0
35.7
33.8
47.6
50.6
47.9
22.2
43.4
9
100
98
44
37
7
295
3.1
33.9
33.2
14.9
12.5
2.4
100.0
64.3
66.2
52.4
49.4
52.1
77.8
56.6
14
151
187
89
71
9
521
2.7
29.0
35.9
17.1
13.6
1.7
100.0
100.0
100.0
100.0
100.0
100.0
100.0
100.0
Univariate analysis
The risk of becoming ill in people reporting consumption of food from vendors at the Street Spice
festival on any day is shown in Table 2. Sachins was the only vendor with a significant positive
association with illness (Risk Ratio (RR) = 8.59, 95% CI 6.08 – 12.14) and explained 89% of the
cases. Consumption of food from the other two vendors for whom detailed food information was
sought (The Rib Man and Monsieur Crepe) were not associated with illness; these were the
second and third most popular vendors, which explains why they appeared often in the exposures
reported to the Environmental Health Department. People reporting consuming foods from The
Rib Man and Paleo were significantly less likely to be ill than people who did not.
Sachins foods were divided into „Standard „and „South Indian‟ foods which were separately
prepared. The risk associated with reported consumption of the South Indian foods (RR = 7.77,
95% CI 6.10 – 9.91) greatly exceeded that for standard menu items (RR=1.69, 95% CI1.42-2.00),
though the latter remained significant. The proportion of cases explained was 80% and 40%
respectively.
The majority of individual food items served from Sachins were significantly associated with illness
(Table 3). Coconut chutney had the highest association (RR 4.39 95% CI3.73-5.17) followed by
Dosa (RR 4.29 95%CI 3.62-5.08), explaining 55% and 59% of the cases respectively. Coconut
chutney was a side dish served with portions of Dosa.
Stratified Analysis
When associations with other vendors were stratified by exposure to South Indian food items, the
significantly low RR for The Rib Man and Paleo became non-significant (data not shown).
37
When Sachins standard food items were stratified by exposure to South Indian foods associations
were reduced (univariate RR 1.69, adjusted RR 1.23) suggesting that confounding between the
different foods had raised the univariate risk ratios (Table 4).
Table 5 shows the effect of stratifying exposure to Sachins food items by coconut chutney. The
associations with illness were similarly reduced.
Interpretation
The response rate achieved by this cohort study is estimated at about 7% of attendees, based on
the organiser estimate of 12,000 attenders in total. This is a small proportion, but not surprising in
view of the difficulties in issuing invitations to a dispersed population attending an event of this
type. The attack rate among responders (35%) was likely to be much higher than in attenders of
the festival as a whole, as people who were ill were more likely to be motivated to respond. The
capture – recapture study (Appendix 3) provides a range of estimates of the overall attack rate of
between 5.2% and 10.2% with a best estimate of 7.7%, equating to 926 cases. Using these
figures the response rate in cases would be estimated as 33%, and the response rate in noncases as 5%. A low response rate in a cohort study may be associated with the introduction of
bias if the respondents are not typical of the cohort as a whole. In particular the methods used to
invite responses might lead to an age-specific differential in response rates. Table 1 shows that
responses were received from a broad range of ages, but there is no estimate of the agedistribution of attendees at the festival available to compare it with.
However there is no obvious mechanism for such potential biases affecting the association found
with an individual vendor, or with differing associations between illness and specific food items
sold by an individual vendor. It is concluded that while the cohort study did not of itself ascertain
meaningful attack rates, the associations with illness (Relative risks) are robust. The capture recapture provides for a somewhat more precise estimate of attack rate.
The univariate associations with South Indian and standard food items from the Sachins stall
strongly suggested that South Indian foods were the main reason that the vendor was associated
with illness. However the standard food items were also significantly associated. The possible
reasons for this are either that they were also genuinely associated with illness, albeit with a lower
level of risk, or that the association was caused by confounding, which could occur because
people who consumed South Indian foods from the vendor and became ill also consumed
standard food items.
Stratified analysis was undertaken to investigate this possibility. Stratification separately
examined the association of standard foods with illness in people who did and did not also eat
South Indian items. If confounding is the cause of the association it should remove the association
with standard items. This analysis found that the association with standard food items was
reduced but remained significant. This shows that at least some of the apparent association was
caused by confounding. The possible explanations for the remaining association are either that
there was a genuine associated risk with the standard food items, or that there was
misclassification between the categories such that survey respondents inaccurately reported
which foods they ate from Sachins. Such misclassification would not be surprising as respondents
may have had difficulty either remembering precisely what they had eaten, or recognising the
description of the food item on the questionnaire. However it is not possible to rule out the
possibility of a risk associated with the standard food items.
When looking at individual food items, the coconut chutney was the item most strongly associated
with illness, but several other foods were also associated. Both confounding and misclassification
are is very likely amongst these foods. Coconut chutney was served as an accompaniment to the
main dishes, predominantly Dosa, so that the univariate risks of these foods would be expected to
38
be very similar through confounding. In addition several of the foods were similar in appearance
and hence likely to be misreported, and furthermore, it is common for people to remember and
report eating a main dish, but to forget or omit to report accompaniments served with it. There is
evidence for this latter phenomenon in that fewer people reported eating the chutney than reported
the dosa it was served along with. These factors are considered to be the likely reason that the
relative risks and proportion of cases explained associated with coconut chutney are lower than for
South Indian dishes as a group, and that for South Indian foods is slightly less than for Sachins as
a whole.
Stratification of individual food items by consumption of coconut chutney greatly reduced the
associations with these other foods, while leaving several significantly associated with illness. As
described above, the possible reasons for this remaining association lie with misclassification – for
example if people ill after consuming coconut chutney did not report consumption on their
questionnaire – or a genuine risk associated with these other food items, or a combination of both.
A genuine risk could occur because of a separate association of that food item with illness, or
because of cross-contamination.
Conclusion
The cohort study demonstrated a risk of illness associated with consuming foods from Sachins on
any day of the festival, and within the items sold with the South Indian foods and within these
items the strongest association was with coconut chutney. The magnitude of the association and
proportion of cases explained very strongly suggest that this association was causal.
It is considered that there is likely to have been misclassification of exposures in survey responses
because of the nature of the food item and that this may explain why the association with this food
item is less than the association for South Indian and all Sachins foods as a group, but cross
contamination between foods cannot be excluded on the basis of this analysis. The study could
not distinguish between these possibilities, but nevertheless provides strong evidence that the
coconut chutney was the main vehicle of infection.
39
Table 2: Risk of becoming ill associated with consumption of food from vendors at the Street Spice festival.
Vendor
Sachins
South Indian foods
Standard foods
The Rib Man
Paleo
El Kantina
Las Paelleras
Rasa Nusantara
Love Food
Pit Stop
Tasty Thai Deli
Manjit's Kitchen
LuLu Chai
Ramside Hall
Papa Ganoush
Bar Popolo
Riley's Fish Shack
David Kennedy
Monsieur Crepe
Heavenly Mana
Wiga Wigaa Chilli's
Electric East
Exposed
Total Cases
414
273
281
244
235
123
230
60
52
12
47
13
73
22
77
36
45
12
59
27
104
36
79
34
60
20
77
31
11
5
116
43
176
65
119
47
200
75
76
29
50
19
159
60
AR%
65.9
86.8
52.3
26.1
23.1
27.7
30.1
46.8
26.7
45.8
34.6
43.0
33.3
40.3
45.5
37.1
36.9
39.5
37.5
38.2
38.0
37.7
Total
404
537
583
594
282
285
292
260
287
288
272
270
285
278
318
281
253
265
624
266
303
253
Unexposed
Cases
31
60
181
246
110
113
117
96
110
108
111
100
114
104
123
110
98
102
230
99
118
97
AR%
7.7
11.2
31.1
41.4
39.0
39.7
40.1
36.9
38.3
37.5
40.8
37.0
40.0
37.4
38.7
39.2
38.7
38.5
36.9
37.2
38.9
38.3
40
Risk
Ratio
95% C.I.
P
value
% of cases
explained
8.59
7.77
1.69
0.63
0.59
0.70
0.75
1.27
0.70
1.22
0.85
1.16
0.83
1.08
1.18
0.95
0.95
1.03
1.02
1.03
0.98
0.98
[6.08-12.14]
[6.10-9.91]
[1.42-2.00]
[0.50-0.80]
[0.35-0.99]
[0.43-1.13]
[0.52-1.10]
[0.95-1.69]
[0.42-1.15]
[0.89-1.67]
[0.63-1.15]
[0.86-1.56]
[0.57-1.22]
[0.79-1.47]
[0.61-2.28]
[0.72-1.25]
[0.74-1.22]
[0.78-1.34]
[0.83-1.25]
[0.74-1.42]
[0.67-1.43]
[0.76-1.27]
0.000
0.000
0.000
0.000
0.028
0.117
0.118
0.121
0.131
0.236
0.271
0.335
0.336
0.649
0.650
0.699
0.705
0.852
0.870
0.881
0.899
0.902
89
80
40
20
4
4
7
12
4
9
12
11
7
10
2
14
21
15
25
9
6
20
Table 3: Risk of becoming ill associated with consumption of individual foods served on the Sachins stall and grouped food
categories.
Section of
Sachins stall
South Indian
South Indian
South Indian
South Indian
Standard
South Indian
Standard
Standard
Standard
Standard
Standard
Standard
Standard
Standard
Standard
Standard
Individual food items
Coconut chutney
Dosa
Uttaphum
Vada
Tamarind sauce
Samba sauce
Yoghurt
Daal
Chickpeas
Mint chutney
Potatoes
Keema pav
Other food
Vegetable pav
Chicken tikka wrap
Chaat
Exposed
Total Cases
188
168
213
182
33
31
61
53
17
15
56
47
27
20
19
14
32
20
21
14
16
11
60
32
9
7
24
14
89
39
57
26
AR%
89.4
85.5
93.9
86.9
88.2
83.9
74.1
73.7
62.5
66.7
68.8
53.3
77.8
58.3
43.8
45.6
Total
619
602
781
753
775
748
776
791
777
785
796
754
818
790
727
757
Unexposed
Cases
126
120
269
247
264
244
270
282
278
279
288
270
299
287
263
275
41
AR%
20.4
19.9
34.4
32.8
34.1
32.6
34.8
35.7
35.8
35.5
36.2
35.8
36.6
36.3
36.2
36.3
Risk
Ratio
4.39
4.29
2.73
2.65
2.59
2.57
2.13
2.07
1.75
1.88
1.90
1.49
2.13
1.61
1.21
1.26
95% C.I.
[3.73-5.17]
[3.62-5.08]
[2.40-3.11]
[2.30-3.05]
[2.12-3.16]
[2.21-3.00]
[1.67-2.71]
[1.55-2.75]
[1.31-2.32]
[1.37-2.57]
[1.35-2.68]
[1.15-1.92]
[1.48-3.05]
[1.13-2.28]
[0.94-1.56]
[0.93-1.69]
P
value
0.000
0.000
0.000
0.000
0.000
0.000
0.000
0.001
0.002
0.003
0.007
0.007
0.011
0.028
0.159
0.161
% of cases
explained
55
59
10
17
5
15
7
5
7
5
4
10
2
5
13
8
Section of
Sachins stall
Both
South Indian
South Indian
Both
Both
South Indian
Standard
Standard
Standard
Food group consumed
Main and/or Side
dishes
Main and/or Side
dishes
Main dishes
Main dishes
Side dishes
Side dishes
Side dishes
Main and/or Side
dishes
Main dishes
Exposed
Total Cases
AR%
Unexposed
Total Cases
AR%
Risk
Ratio
95% C.I.
P
% of cases
explained
414
273
65.9
404
31
7.7
8.59
[6.08-12.14]
0.000
89
281
244
86.8
537
60
11.2
7.77
[6.10-9.91]
0.000
80
275
390
250
198
87
238
259
203
175
60
86.6
66.4
81.2
88.4
69.0
543
428
568
620
731
66
45
101
129
244
12.2
10.5
17.8
20.8
33.4
7.12
6.32
4.57
4.25
2.07
[5.65-8.97]
[4.75-8.40]
[3.79-5.50]
[3.61-4.99]
[1.74-2.46]
0.000
0.000
0.000
0.000
0.000
78
85
66
57
20
235
123
52.3
583
181
31.1
1.69
[1.42-2.00]
0.000
40
188
86
45.7
630
218
34.6
1.32
[1.09-1.60]
0.006
28
42
Stratified analysis
Table 4: Risk of becoming ill associated with consumption of Sachin Standard food items stratified by exposure to any South Indian
item
Section of
Sachins stall
Food group
Standard
Standard
Standard
All
Main dishes
Side dishes
Crude
RR
1.69
1.32
2.07
95% CI
[1.42-2.00]
[1.09-1.60]
[1.74-2.46]
Exposed
Stratum
RR
1.04
1.03
1.03
43
Unexposed
Stratum
RR
2.64
1.98
3.82
M-H adjusted
RR
1.23
1.18
1.23
95% CI
[1.10-1.38]
[1.04-1.33]
[1.10-1.38]
Percentage
change (%)
-26.90
-10.89
-40.37
Table 5: Risk of becoming ill associated with consumption individual food items stratified by exposure to coconut chutney
Section of
Sachins stall
Food
group
Individual food
item
South Indian
South Indian
South Indian
Standard
South Indian
Standard
Main dish
Main dish
Main dish
Side dish
Side dish
Side dish
-
-
Standard
Standard
Standard
Standard
Standard
Standard
Standard
Side dish
Side dish
Side dish
Side dish
Main dish
Main dish
Main dish
Standard
Main dish
Dosa
Uttaphum
Vada
Tamarind sauce
Samba sauce
Yoghurt
Other sachins
food
Daal
Potatoes
Mint chutney
Chickpeas
Vegetable pav
Keema pav
Chaat
Chicken tikka
wrap
RR
4.29
2.73
2.65
2.59
2.57
2.13
95% CI
[3.62-5.08]
[2.40-3.11]
[2.30-3.05]
[2.12-3.16]
[2.21-3.00]
[1.67-2.71]
Exposed
Stratum
RR
0.99
1.08
0.95
1.14
0.97
1.13
2.13
[1.48-3.05]
1.12
3.31
1.44
[1.20-1.74]
-32.15
2.07
1.9
1.88
1.75
1.61
1.49
1.26
[1.55-2.75]
[1.35-2.68]
[1.37-2.57]
[1.31-2.32]
[1.13-2.28]
[1.15-1.92]
[0.93-1.69]
1
1.13
0.87
1.13
1.13
1.04
1.04
3.07
2.51
2.97
2.04
1.66
2.12
1.54
1.41
1.56
1.36
1.41
1.28
1.48
1.25
[1.13-1.77]
[1.21-2.01]
[1.03-1.79]
[1.14-1.75]
[1.01-1.61]
[1.20-1.82]
[0.98-1.59]
-31.67
-18.04
-27.76
-19.14
-20.56
-0.7
-0.6
1.21
[0.94-1.56]
1.03
1.26
1.12
[0.92-1.36]
-7.75
Crude
44
Unexposed
Stratum
RR
5.69
4.63
4.71
2.99
3.16
2.91
RR
1.92
1.38
1.28
1.32
1.08
1.64
95% CI
[1.73-2.13]
[1.26-1.52]
[1.15-1.44]
[1.17-1.47]
[0.95-1.22]
[1.37-1.96]
M-H adjusted
Percentage
change (%)
-55.23
-49.26
-51.49
-49.2
-58.05
-22.96
Appendix 2 – Case follow-up study (survey 2)
Aim
To document the symptomatology and some aspects of the burden of illness associated with the
outbreak
Methods
A second survey directed at known cases of illness in attenders to the Street Spice festival was
undertaken in order to obtain further details of the symptoms experienced and some measures of
the burden of illness. This was administered using an online survey using the same
SelectSurvey.Net application described in survey 1.
A list of people reporting illness was collated from three sources; the Newcastle City Council
Environmental Health Department list of people who had reported illness after attendance to
themselves or other local authorities; people reporting illness in response to survey 1; and people
who had had relevant specimens submitted to laboratories for testing having attended the festival.
Available contact details were obtained from the de-duplicated list and each case contacted.
The survey was sent by personalised email where email addresses were available; the emails
contained a unique link to the survey leading to a personalised questionnaire which was pre-filled
with information that had been given in previous answers given by that respondent to the
questions e.g. name. Where no email address was supplied, a letter containing a nonpersonalised link to the survey was posted to the case. A total of 527 invitations were sent, 361 by
email and 165 by post. A reminder email/letter was sent two weeks after the first contact. For any
cases reporting continuing illness, a further follow-up email was sent two weeks after the survey
was closed to ascertain the duration of illness.
The questionnaire asked respondents for detailed information about their symptoms, time off work
and use of healthcare.
Data from the questionnaire were downloaded and analysed using STATA 12 (StataCorp). The
case definition used in the analysis was the same as for the cohort study; cases were defined as
anyone attending the Street Spice Food Festival that experienced diarrhoea between 12 hours
and 5 days after attending.
The survey was opened on the 28th March, the reminder was sent on the 15th of April and the
survey was closed on the 29th of April.
Results
There were 374 responses, a 71% response rate, of whom 351 met the study case definition and
were included in the analyses. This exceeded the number of cases in the first survey.
Symptomatology is shown in table 6. Diarrhoea formed part of the case definition; in addition 91%
reported abdominal pain, 58% nausea and 18% vomiting. Fever was reported by 44%. Diarrhoea
was the most prolonged symptom, with median duration of 11 days and range at the time of the
survey of 1-49 days; at that time 14 of 351 (4.0%) of cases had on-going diarrhoea. Abdominal
pain also had a long duration with a median of 7 days and 11 people reporting continuing illness.
There were relatively low numbers of cases reporting vomiting, 18% of cases, of those that
reported vomiting it was short lived with a median of 1 day.
Fifty-eight cases (16.6%) reported a relapse of symptoms. The second episode of diarrhoea were
on average shorter than the first; first episode median duration 9 days, second episode median
duration 4 days (Table 7)
45
Almost two thirds of cases visited any healthcare setting for their illness (table 8) and the mean
number of visits to any setting was 2.3. General practitioners were the most frequently consulted
with 41% of cases reporting attending for a mean of 1.5 visits. Two cases (0.53%) reported
hospital admission and a further 6 visited hospitals without admission (Table.
One third of cases said they had contacted the Environmental Health Department (Table 9);
however from Environmental Health records we know that more than twice this number actually
did so. One fifth reported contacting the Health Protection Agency.
Workdays were reported as missed by 207 cases, 59% of all cases and 70% of those in work
(Table 10). The average number of days missed by these cases was 4.9. The adjusted estimate of
the total number of cases from capture re-capture was 814 (See Appendix 3), applying the same
percentage of people who had days off work and the mean number of days missed, produces an
estimate that the total number of days of work lost was 2363 days.
Interpretation
Symptomatology was broadly consistent with Salmonella infection, but also with a range of other
organisms causing gastro-intestinal disease. The duration of symptoms and relapse rate were
higher than expected (Tables 6 & 7). The proportion of cases admitted was low (Table 8)
compared with many other outbreaks and sporadic cases in the community. This suggests that
only a small proportion experienced very severe disease; this may be a characteristic of the
organism(s) causing disease, but in addition it may reflect that the affected population, people
attending a food festival, were a relatively health population not at high risk for food borne illness.
However the use of other healthcare facilities, the percentage of respondents who missed work,
(70%) and the amount of working time lost by them (median 3.2 days; total of 995 days)
demonstrates that the disease nevertheless caused very significant illness and disruption to
normal life.
Extrapolating the working days lost to the population estimated by the capture re-capture study,
produces an estimate that the total number of days off work was 2363 days. This figure should be
treated with some caution as it may be that people who suffered more prolonged symptoms were
more likely to have provided responses; however a significant fraction of the estimated number of
affected people responded to the survey.
Conclusion
The case follow-up study provided in depth information about symptoms experienced by the cases
and the burden of illness. The pattern of symptoms is similar to that previously reported in
Salmonella outbreaks, although the duration of symptoms was longer than expected. It is also
compatible with illness caused by other organisms, including the entero-aggregative E. coli found
by PCR testing. There were also reports of relapse of symptoms. There was a high degree of
contact with healthcare for the cases but the hospitalisation rate was very low.
46
Table 6: Symptoms and duration of illness from case follow-up study
Median
Duration
Symptom
Number Percentage
duration
range
Diarrhoea
351
100
11
1-49*
still ill
14
25-49*
27
not still ill
337
1-43
11
Abdominal pain
320
91
7
1-47*
still ill
11
14-47*
34
not still ill
308
1-34
7
Nausea
203
58
3
1-28
Fever
155
44
2
1-14
Vomiting
64
18
1
1-6
Table 7: Relapse of symptoms
Category
First episode
Second episode
Days to relapse
Total days with
diarrhoea
Number
Percentage
350
58
58
100
16.6%
-
351
10.9
5.5
3.8
Median
duration
(days)
9
4
2
Range of
duration
(days)
1-49
2-16
1-26
11.6
10
1-49
Mean duration
(days)
Table 8: Healthcare seeking behaviour
Number of cases
Healthcare setting
Percentage
Mean times visited/contacted
attended/ sought advice
Any of the settings
227
64.7
2.30
GP
143
40.7
1.48
NHS Direct
42
12.0
1.14
Walk-in Centre
16
4.6
1.06
Hospital -any
8
2.3
1.25
Hospital -admission
2
0.53
The mean number of settings visited or contacted was 1.77, with a range of one to five settings.
47
Range times visited/contacted
1-8
1-5
1-3
1-2
1-3
-
Table 9: Contacting Health Protection Agencies
Number of cases
Public Health Agencies
attended/ sought
Percentage
advice
EH department
123
35.0
HPA
70
19.9
Mean times
visited
Range times
visited
1.31
1.14
1-5
1-4
Table 10: Days off work
Off work
Number
Percentage
Percentage of
those working
Yes
No
N/A not working
Total
207
89
55
351
59
25
16
100
70
30
100
Mean days off work: 4.92 days
Median days off work: 3.5 days
Range days off work: 1-35
Total number of days off work: 995 (N=202, 5 cases who missed work did not give the number of days missed)
48
Appendix 3 – Capture Re-capture Study
Aims
To identify the true size of the outbreak in order to more accurately estimate the attack rate and
burden of associated illness and potential for bias within the cohort study.
Methods
A three source capture re-capture analysis was undertaken. The three datasets used were; people
proactively contacting the Environmental Health department; people reporting illness in the cohort
study (survey 1); and people attending the festival for whom a sample was sent to a laboratory
after a health services contact. Cohort study cases were not restricted to the cohort study case
definition. After data cleaning and standardisation all sources were fuzzy matched using
algorithms based on forename, surname and date of birth within FEBRL, an open source fuzzy
matching application. Results were verified by a manual check.
The resultant dataset contained a list of unique individuals and the source(s) in which they they
were found. Capture re-capture analysis was then undertaken on this dataset. Wittes method was
used to undertake 2 source estimates and to test for independence using Excel (Microsoft). A
saturated loglinear model using Poisson regression used as calculate the final model in STATA 12
12 (StataCorp) to estimate the number of uncaptured cases and total number of cases.
Results
Table 11 shows the number of individuals in each of the three data sources and Figure 2 (left hand
diagram) illustrates the distribution of individuals between them.
Tests for independence were undertaken using Wittes method (Table 12). The odds ratios show
that the datasets were not independent and that there were significant positive associations
between two of the three pairs of datasets. The third pair (Environment Health/Survey within Lab)
had OR of 1.4 with wide confidence intervals.
The saturated loglinear model was therefore chosen for the final model. The central estimate of
the numbers of people ill not captured by any source was 334, and the estimated total number of
cases was 926. Confidence intervals were broad: 95% CI were 628 – 1224.
Applying the ratio of cases to people reporting illness implied by the cohort study case definition
would reduce these estimates to 88% of the values reported above; central estimate to 814, with
range 552 to 1076.
Interpretation and Conclusions
Three source capture –recapture enables estimation of the true size of the population from which
people reporting illness arose despite the data sources not being completely independent; i.e.
where it is more likely that an individual is in a data source if they are in another.
The main estimates in this study were undertaken using a broader case definition than in the
cohort study (survey 1) which excluded non-diarrhoeal illness and specified an onset period of 12
hours to 5 days after exposure. It would not have been possible to apply the case definition to the
other data sources; however it was considered that all gastrointestinal illness was the best
definition to use to estimate the total burden of illness. The purpose of the restrictive case
definition used the cohort study was to reduce the risk of including any unrelated illnesses within
the case group. However this definition may also exclude related cases of illness, falsely reducing
any estimate of the numbers of cases associated with an outbreak. Approximately 10% of people
reporting gastro-intestinal illness to the survey did not meet the cohort study definition; this group
reported similar incubation periods to those within the case definition and it was considered
49
probable that many were cases of illness genuinely associated with the festival. The estimates
should therefore be interpreted as an estimate of the numbers of cases of illness occurring after
attendance at the festival, with the recognition that some of this estimate may reflect background
cases of illness which may have occurred irrespective of attendance. Applying the proportion of
people reporting illness in survey 1 who met the cohort study case definition to the final estimates
provides an adjusted estimate of the numbers of cases diarrhoeal illness with the specified
incubation period.
Using the central estimate (926), the estimated sensitivity of the individual data sources in respect
of people experiencing gastro intestinal illness after attendance was 44% for reports to the
Environmental Health department, 38% for cohort survey responses, and 15% for laboratory
specimens (Table 13) and 64% for the combined dataset.
The 95% confidence intervals around the central estimate are wide however, ranging from 628 to
1224. This compares with an estimated number of served portions for the suspect food of 900 –
1000; if this equated to a number of people consuming the item it would suggest the attack rate for
any gastro intestinal illness associated with the suspected food items must be above 62.5% and
could be 100%, and for illness meeting the cohort study case definition was 55% to 100%
However it is possible that the numbers of people consuming the items is more than the number
served, as some people may have shared items, and the possibility of cross contamination of
other foods could also increase the numbers exposed. These estimates must therefore be treated
with caution. The corresponding estimates for the illness attack rate in all festival attenders are
between 5.2% and 10.2% with a best estimate of 7.7%.
50
Table 11: Number of cases by route reported
Reported by
Cases
Cohort study (survey 1)
EH department
Lab
348
406
136
Combined Dataset
592
Figure 2: Matched cases by source dataset
EHO (406)
Survey (348)
182
117
Cases not captured (334)
157
334
60
47
14 .
15
Lab (136)
Estimated number of cases missed = 334
Estimated total number of cases = 926 (95% CI: 628 – 1224)
Table 12 Tests for independence
Analysis
Odds
p value
Ratio (Fisher’s exact)
Survey/EHO inside
1.4
0.530
Lab
Survey/Lab inside
2.0
0.003
EHO
EHO/Lab inside
5.8
0.000
Survey
Table 13: Sensitivity of Data Sources for people reporting gastrointestinal illness
Sensitivities
Survey
EHO
Lab
Combined
Estimate
38%
44%
15%
64%
95% C.I Lower
55%
65%
22%
94%
95% C.I Upper
28%
33%
11%
48%
52
Appendix 4: Street Spice outbreak 8168: Food sample results
Sample Description
Date
Submitted
Coconut Milk Powder
08.03.13
Asafoetida
08.03.13
Desicated Coconut
07.03.13
Salmonella
Not
detected
Not
detected
Not
detected
Coconut Milk Powder
06.03.13
Not
detected
< 20
< 3 (MPN)
< 10
< 10
< 20
< 20
Whole Green Chilli
06.03.13
Not
detected
< 10
< 10
> 90000
< 10
< 20
< 20
Fresh Corriander
06.03.13
Not
detected
< 10
< 10
> 150000
< 10
Presumptive
Presumptive
Birdseye Whole
Green Chilli
06.03.13
Not
detected
< 10
200
Presumptive
< 10
< 20
< 20
Fresh Ginger
06.03.13
Not
detected
< 10
< 20
95000
< 10
Presumptive
Presumptive
Dried Curry Leaves *
06.03.13
Detected
O:4 H:g *
< 10
> 1100
150000
Presumptive
Presumptive
Presumptive
Urad Dall
06.03.13
Not
detected
< 20
< 3 (MPN)
< 10
< 10
< 20
< 20
Dried Basmati Rice
06.03.13
Not
detected
< 20
< 3 (MPN)
< 10
< 10
< 20
< 20
06.03.13
Not
detected
< 20
< 3 (MPN)
< 10
< 10
Presumptive
Presumptive
Dried Long Grain Rice
Swab Uncooked Rice
Container
Swab Uncooked Rice
Container
06.03.13
L.
monocytogenes
< 20
E. coli
Enterobacteriaceae
C.
perfingens
Bacillus spp
Bacillus spp
< 20
<5
< 10
< 20
< 20
< 20
E. coli
O157
< 20
Not
detected
Not
detected
Not
detected
Not
detected
Not
detected
Not
detected
Not
detected
Not
detected
Not
detected
< 10
53
< 20
< 20
< 20
< 20
< 20
< 20
< 20
< 20
Not tested
< 20
Not
detected
06.03.13
S. aureus
Swab Uncooked Rice
Container
06.03.13
Swab Prep Bench
06.03.13
Swab Prep Bench
06.03.13
Swab Prep Bench
Swab Shelf Above
Prep Bench
06.03.13
Swab Shelf Above
Prep Bench
Swab Shelf Above
Prep Bench
Toor Dall
Not
detected
< 20
< 10
< 20
Not
detected
Not
detected
06.03.13
< 20
< 10
< 20
Not
detected
06.03.13
06.03.13
Not
detected
06.03.13
Not
detected
< 20
< 3 (MPN)
< 10
< 10
< 20
< 20
Not
detected
< 20
* the curry leaves were originally recorded as “dried” but it was confirmed on later checking that fresh leaves had been sampled
54
Alert sent to GPS in North East – 6 March 2013
Appendix 5: Outbreak communications materials
North East
06/03/2013
Dear Doctor
Gastrointestinal illness associated with the Street Spice Festival, Newcastle
The Health Protection Unit is investigating reports of gastrointestinal illness associated with the
Street Spice food festival held at Times Square in Newcastle between 28/02/2013 and
02/03/2013. Cases have been reported across the North East.
In order to assist with this investigation we would be grateful if you would:


Formally notify any cases of suspected food poisoning associated with this event
Arrange for your patient to submit a faecal specimen.
o Please clearly label the request form with “ILOG 8168 – for processing at HPA lab,
Newcastle”
o Submit specimens through your usual route
Thank you for your help. Please do not hesitate to contact the HPU if you require any further
information.
Yours sincerely
Dr Kirsty Foster
Consultant in Health Protection
North East Health Protection Unit
Letter sent to people with negative stool sample results – sent from 13 March 2013
Health Protection Agency North East
Our Ref: kf/td 200313
2nd Floor
March 2013
Citygate
Gallowgate
Newcastle upon Tyne
NE1 4WH
Tel 0844 225 3550
Fax (0191) 221 2584
Dear Patient
www.hpa.org.uk
Street Spice Outbreak – Information for People with Negative Lab Results
I am writing with the results of the faecal (stool) sample that you submitted as part of the
investigation into illness associated with the Street Spice Festival in Newcastle. The sample
that you submitted was negative for Salmonella (and also E coli O157, campylobacter and
shigella which were also tested).
What this means:
This means that Salmonella bacteria have not been grown from the sample that you submitted.
Does this mean that I didn’t have Salmonella?
Not necessarily – it only means that the laboratory did not identify Salmonella from your sample.
This can be for a number of reasons:



Sometimes it can be difficult to grow bacteria in the laboratory
The amount of Salmonella can vary between different samples in the same
person and there may not have been sufficient bacteria in your sample to identify
Salmonella
You can still have symptoms after initial infection has gone
Why have only a small number of people tested positive for Salmonella?
Over 300 people have reported being ill. However not all of these people have submitted a
specimen. For the reasons given above, not all of the samples from those who have been
unwell will be positive. This is the case in most outbreak investigations.
Does this mean that tests were not reliable?
No – samples are processed using the standard accredited tests used by all microbiology
laboratories.
What does a negative result mean for the investigation of this outbreak?

The investigation of human specimens forms only one part of the investigation. We
also look closely at the symptoms people have had and what they have reported
eating including the online survey which you may have completed. Samples of food
are also investigated.

As you are likely to be aware from the media, the investigation into this outbreak is
still ongoing.

You will still be considered as a case because you became unwell with symptoms of
food poisoning after visiting the Street Spice Festival.
What should I do if I am still unwell?

The symptoms of Salmonella and other types of food poisoning include abdominal
pain and cramps, diarrhoea and vomiting. These are unpleasant but most people
recover within about a week. You should not return to work or school for 48 hours
after your last symptoms of diarrhoea or vomiting. Contact your own GP if your
symptoms are not improving or are getting worse.
Yours sincerely
Dr Kirsty Foster
Consultant in Health Protection
On behalf of the Outbreak Control Team
Update on investigation sent to people reporting illness – sent 21 March 2013
Information about on-going investigation into reports of illness following Street Spice festival
We are aware that you reported illness that occurred after you attended the Street Spice Festival in
Newcastle between 28 February and 2 March 2013 or completed the on-line survey.
The investigation is on-going but we thought that it would be helpful to update you on the progress of
the investigation and the infection identified.
Update on findings to date:
We have identified Salmonella from a number of people who have been ill and have found the same
strain of Salmonella in one of the food ingredients used at the festival.
More detailed information about these findings, including the results of the food samples, will be made
public once it is clear that this will not prejudice any formal actions that Newcastle City Council may
decide to take.
As part of the investigation, we are looking at all ways in which the food could have become
contaminated with Salmonella and whether there have been any breaches of food safety legislation
where further action may be necessary.
We do not believe there is an on-going risk to the public’s health following this outbreak, but are
working closely with organisations including the Food Standards Agency to ensure that any necessary
actions are taken and advice given.
The information below describes the process of outbreak investigation and the next steps in our
investigation; we have also provided some information about Salmonella infection.
The investigation
Following reports of illness from people who attended the Street Spice Festival, a multi-agency outbreak
control team has been working to identify the cause of illness and the possible source of infections. The
outbreak control team has representatives from different departments of the Health Protection Agency
and Newcastle City Council.
Over 400 people have now contacted the Environmental Health (EH) department at Newcastle City
Council to report illness (mainly diarrhoea and abdominal pain but some also had vomiting and fever).
Information has been collected from everyone who contacted the EH department about the foods they
ate at the festival and the day(s) they attended. A number of people have submitted faecal (stool)
specimens which have undergone standard tests for common causes of these symptoms.
The outbreak control team has been gathering information from a wide range of sources including
people who have been ill, the vendors who had stalls at the festival, the online survey and from food
samples collected from vendors at the event.
All this information is being brought together to try to establish the cause of the illness, inform the
control measures that are put in place to prevent any further cases of illness and to guide any further
action that may be needed.
The illness
It is not unusual in an outbreak investigation that some people who have been ill have a ‘negative’ result
from the samples given and there are several reasons for this. The amount of Salmonella can vary
between different samples in the same person, there may be insufficient bacteria in a sample to identify
Salmonella and it can sometimes be difficult to grow the bacteria in the laboratory. Also, people can
continue to have symptoms after the initial infection has resolved.
However, in the investigation of an outbreak we classify people as ‘cases’ based on a number of factors
including laboratory results, the symptoms and timing of illness that they describe and the ‘exposures’
they have had to a possible source of infection, in this case eating at the Street Spice event.
We are aware that some people have had prolonged symptoms of diarrhoea and abdominal pain – this
can happen with Salmonella infection. If you are concerned about on-going symptoms, please contact
your GP for clinical advice.
We have shared information about the outbreak with GPs and hospitals across the region so they are
aware of our findings to date.
What happens next?
Whilst we appreciate that people who have been unwell are keen to understand what has caused the
outbreak, the outbreak control team must be confident that all the relevant information has been
thoroughly reviewed before making findings public. As noted above, the formal legal investigation into
the outbreak is continuing and it is important that this is not prejudiced by the early release of detailed
information on findings.
When the outbreak investigation is finished, a report will be produced by the outbreak control team.
Due to the size and complexity of the investigation, this report will take 6 - 8 weeks to compile.
We have made every effort to send this update to everyone who reported illness following the event. If
you attended the event as part of a group / party, please share this information with anyone else who
may have been affected.
.
Dr Kirsty Foster
Consultant in Health Protection, North East Health Protection Unit
Chair of the Outbreak Control Team, 21 March 2013
Information to cases re follow-up study – sent 28 March 2013
Street Spice Food Festival – further investigation into health effects
We are contacting you because you reported illness after the Street Spice Festival to
the Environmental Health team in Newcastle.
The type of Salmonella that has been identified from the outbreak investigation is
uncommon and some people have reported that they have been unwell for more
than a week. This is unusual and we would like to ask some further questions so
that we can get a better understanding of the health effects of this particular
infection.
The link below is for a survey to further investigate the symptoms and duration of
illness in people that attended the Street Spice Food Festival. Please be assured
that all information will be treated with the strictest of confidence. The survey
should take less than 10 minutes of your time.
The link to the survey is:
http://tinyurl.com/streetspice2
The survey will be open until 9am on Monday 22 April.
As outlined in the update that was sent out last week, the outbreak investigation is
still on-going. Newcastle City Council’s Environmental Health team may contact you
again as part of the on-going investigation into the source of the outbreak.
Thank you, in advance, for responding to the survey
Dr Kirsty Foster
Consultant in Health Protection, North East Health Protection Unit
On behalf of the Street Spice Outbreak Control Team
28 March 2013
Letters sent to cases with positive PCR results
Letter for cases with pcr +ve result for EAEC
Dear
Street Spice Festival investigation - Update on results and publication of
outbreak report
I wrote to you in March about the result of the stool sample you submitted as part of
the investigation of illness associated with the Street Spice Festival. I am writing to
you again to give you an update on the latest results and to inform you that the
outbreak investigation report is being published today.
As you will know from the previous update we sent to people who had reported
illness, we detected an unusual strain of salmonella in samples from human cases
and from a food ingredient used at the event.
However, the number of confirmed salmonella cases we identified was relatively
small considering the number of people reporting symptoms. In addition, many
people suffered symptoms for longer than we typically see with salmonella infection.
The laboratory tests normally undertaken had not detected organisms other than
salmonella, so we arranged for samples to be tested for other organisms using a
new technique, called the polymerase chain reaction or PCR, which is still in
development. At present, this PCR is not part of the standard clinical tests used for
the diagnosis of gastro-intestinal infection so any results have to be interpreted with
caution.
Many of the samples tested using the new technique were positive for Enteroaggregative E Coli and Shigella, both these organisms are associated with travellers‟
diarrhoea and causes symptoms such diarrhoea and abdominal cramp / pain which
were similar to the symptoms many people reported in this outbreak. Affected
individuals usually make a full recovery from such infections with no long term
effects.
Your sample was one of these that tested positive which suggests you may have
been infected with Entero-aggregative E Coli.
We were not able to test food samples from the Festival using these techniques, so
we cannot demonstrate that the Entero-aggregative E.coli or Shigella organisms
were in food at the festival.
The outbreak report which we are publishing today includes a discussion of the
significance of these findings. It concludes that this was a large outbreak of gastrointestinal illness, with Salmonella Agona PT 40 confirmed in 25 cases and also
isolated from a food ingredient used at the event. It goes on to explain that findings
from further advanced laboratory analysis suggest that other organisms, including
Entero-aggregative E Coli and Shigella, may also have contributed to the burden of
illness experienced by people who attended the event.
Letters sent to cases with positive PCR results
I have enclosed a copy of the Executive Summary of the report with this letter. If you
would like a copy of the full report, it is available on the Newcastle Council website.
I‟d like to thank you for your co-operation with this complex investigation.
Yours sincerely
Dr Kirsty Foster
Consultant in Health Protection / Chair of Outbreak Control Team
Letters sent to cases with positive PCR results
Letter for cases with pcr +ve result for Shigella
Dear
Street Spice Festival investigation - Update on results and publication of
outbreak report
I wrote to you in March about the result of the stool sample you submitted as part of
the investigation of illness associated with the Street Spice Festival. I am writing to
you again to give you an update on the latest results and to inform you that the
outbreak investigation report is being published today.
As you will know from the previous update we sent to people who had reported
illness, we detected an unusual strain of salmonella in samples from human cases
and from a food ingredient used at the event.
However, the number of confirmed salmonella cases we identified was relatively
small considering the number of people reporting symptoms. In addition, many
people suffered symptoms for longer than we typically see with salmonella infection.
The laboratory tests normally undertaken had not detected organisms other than
salmonella, so we arranged for samples to be tested for other organisms using a
new technique, called the polymerase chain reaction or PCR, which is still in
development. At present, this PCR is not part of the standard clinical tests used for
the diagnosis of gastro-intestinal infection so any results have to be interpreted with
caution.
Many of the samples tested using the new technique were positive for Enteroaggregative E Coli and Shigella, both these organisms are associated with travellers‟
diarrhoea and causes symptoms such diarrhoea and abdominal cramp / pain which
were similar to the symptoms many people reported in this outbreak. Affected
individuals usually make a full recovery from such infections with no long term
effects.
Your sample was one of these that tested positive which suggests you may have
been infected with Shigella.
We were not able to test food samples from the Festival using these techniques, so
we cannot demonstrate that the Entero-aggregative E.coli or Shigella organisms
were in food at the festival.
The outbreak report which we are publishing today includes a discussion of the
significance of these findings. It concludes that this was a large outbreak of gastrointestinal illness, with Salmonella Agona PT 40 confirmed in 25 cases and also
isolated from a food ingredient used at the event. It goes on to explain that findings
from further advanced laboratory analysis suggest that other organisms, including
Entero-aggregative E Coli and Shigella, may also have contributed to the burden of
illness experienced by people who attended the event.
Letters sent to cases with positive PCR results
I have enclosed a copy of the Executive Summary of the report with this letter. If you
would like a copy of the full report, it is available on the Newcastle Council website.
I‟d like to thank you for your co-operation with this complex investigation.
Yours sincerely
Dr Kirsty Foster
Consultant in Health Protection / Chair of Outbreak Control Team
Letters sent to cases with positive PCR results
Letter for cases with pcr +ve result for EAEC and Shigella
Dear
Street Spice Festival investigation - Update on results and publication of
outbreak report
I wrote to you in March about the result of the stool sample you submitted as part of
the investigation of illness associated with the Street Spice Festival. I am writing to
you again to give you an update on the latest results and to inform you that the
outbreak investigation report is being published today.
As you will know from the previous update we sent to people who had reported
illness, we detected an unusual strain of salmonella in samples from human cases
and from a food ingredient used at the event.
However, the number of confirmed salmonella cases we identified was relatively
small considering the number of people reporting symptoms. In addition, many
people suffered symptoms for longer than we typically see with salmonella infection.
The laboratory tests normally undertaken had not detected organisms other than
salmonella, so we arranged for samples to be tested for other organisms using a
new technique, called the polymerase chain reaction or PCR, which is still in
development. At present, this PCR is not part of the standard clinical tests used for
the diagnosis of gastro-intestinal infection so any results have to be interpreted with
caution.
Many of the samples tested using the new technique were positive for Enteroaggregative E Coli and Shigella, which are both organisms usually associated with
travellers‟ diarrhoea and cause symptoms such diarrhoea and abdominal cramp /
pain which were similar to the symptoms many people reported in this outbreak.
Affected individuals usually make a full recovery from such infections with no long
term effects.
Your sample was one of these that tested positive which suggests you may have
been infected with Entero-aggregative E Coli and Shigella.
We were not able to test food samples from the Festival using these techniques, so
we cannot demonstrate that the Entero-aggregative E.coli or Shigella organisms
were in food at the festival.
The outbreak report which we are publishing today includes a discussion of the
significance of these findings. It concludes that this was a large outbreak of gastrointestinal illness, with Salmonella Agona PT 40 confirmed in 25 cases and also
isolated from a food ingredient used at the event. It goes on to explain that findings
from further advanced laboratory analysis suggest that other organisms, including
Entero-aggregative E Coli and Shigella, may also have contributed to the burden of
illness experienced by people who attended the event.
Letters sent to cases with positive PCR results
I have enclosed a copy of the Executive Summary of the report with this letter. If you
would like a copy of the full report, it is available on the Newcastle Council website.
I‟d like to thank you for your co-operation with this complex investigation.
Yours sincerely
Dr Kirsty Foster
Consultant in Health Protection / Chair of Outbreak Control Team
Letters sent to cases with positive PCR results
Letter for cases with EAEC pcr and salmonella culture +ve results
Dear
Street Spice Festival investigation - Update on results and publication of
outbreak report
I wrote to you in March because you reported illness after visiting the Street Spice
Festival in Newcastle. I am writing to you again to give you an update on the latest
results and to inform you that the outbreak investigation report is being published
today.
As you will be aware, Salmonella was identified by standard laboratory tests in the
stool sample you submitted. However, further testing has identified that you may also
have been infected with another bacteria called Entero-aggregative E Coli.
As you will know from the previous update we sent to people who had reported
illness, we detected an unusual strain of salmonella in samples from human cases
and from a food ingredient used at the event. However, the number of confirmed
salmonella cases we identified was relatively small considering the number of people
reporting symptoms. In addition, many people suffered symptoms for longer than we
typically see with salmonella infection.
The laboratory tests normally undertaken had not detected organisms other than
salmonella, so we arranged for samples to be tested for other organisms using a
new technique, called the polymerase chain reaction or PCR, which is still in
development. At present, this PCR is not part of the standard clinical tests used for
the diagnosis of gastro-intestinal infection so any results have to be interpreted with
caution.
Many of the samples tested using the new technique were positive for Enteroaggregative E Coli and Shigella, which are both organisms usually associated with
travellers‟ diarrhoea and causes symptoms such as diarrhoea and abdominal cramp
/ pain which were similar to the symptoms many people reported in this outbreak.
Affected individuals usually make a full recovery from such infections with no long
term effects.
Your sample was one of these that tested positive which suggests you may also
have been infected with Entero-aggregative E Coli. This does not affect your
positive Salmonella result, but suggests that you may have been infected with two
different organisms. It is possible for this to occur and more information is included
in the outbreak report.
We were not able to test food samples from the Festival using these techniques, so
we cannot demonstrate that the Entero-aggregative E.coli or Shigella organisms
were in food at the festival.
The outbreak report which we are publishing today includes a discussion of the
significance of these findings. It concludes that this was a large outbreak of gastro-
Letters sent to cases with positive PCR results
intestinal illness, with Salmonella Agona PT 40 confirmed in 25 cases and also
isolated from a food ingredient used at the event. It goes on to explain that findings
from further advanced laboratory analysis suggest that other organisms, including
Entero-aggregative E Coli and Shigella, may also have contributed to the burden of
illness experienced by people who attended the event.
I have enclosed a copy of the Executive Summary of the report with this letter. If you
would like a copy of the full report, it is available on the Newcastle Council website.
I‟d like to thank you for your co-operation with this complex investigation.
Yours sincerely
Dr Kirsty Foster
Consultant in Health Protection / Chair of Outbreak Control Team
Letters sent to cases with positive PCR results
Letter for cases with Shigella pcr and salmonella culture +ve results
Dear
Street Spice Festival investigation - Update on results and publication of
outbreak report
I wrote to you in March because you reported illness after visiting the Street Spice
Festival in Newcastle. I am writing to you again to give you an update on the latest
results and to inform you that the outbreak investigation report is being published
today.
As you will be aware, Salmonella was identified by standard laboratory tests in the
stool sample you submitted. However, further testing has identified that you may also
have been infected with another bacteria called Shigella.
As you will know from the previous update we sent to people who had reported
illness, we detected an unusual strain of salmonella in samples from human cases
and from a food ingredient used at the event. However, the number of confirmed
salmonella cases we identified was relatively small considering the number of people
reporting symptoms. In addition, many people suffered symptoms for longer than we
typically see with salmonella infection.
The laboratory tests normally undertaken had not detected organisms other than
salmonella, so we arranged for samples to be tested for other organisms using a
new technique, called the polymerase chain reaction or PCR, which is still in
development. At present, this PCR is not part of the standard clinical tests used for
the diagnosis of gastro-intestinal infection so any results have to be interpreted with
caution.
Many of the samples tested using the new technique were positive for Enteroaggregative E Coli and Shigella, which are both organisms usually associated with
travellers‟ diarrhoea and causes symptoms such as diarrhoea and abdominal cramp
/ pain which were similar to the symptoms many people reported in this outbreak.
Affected individuals usually make a full recovery from such infections with no long
term effects.
Your sample was one of these that tested positive which suggests you may also
have been infected with Shigella. This does not affect your positive Salmonella
result, but suggests that you may have been infected with two different organisms. It
is possible for this to occur and more information is included in the outbreak report.
We were not able to test food samples from the Festival using these techniques, so
we cannot demonstrate that the Entero-aggregative E.coli or Shigella organisms
were in food at the festival.
The outbreak report which we are publishing today includes a discussion of the
significance of these findings. It concludes that this was a large outbreak of gastrointestinal illness, with Salmonella Agona PT 40 confirmed in 25 cases and also
Letters sent to cases with positive PCR results
isolated from a food ingredient used at the event. It goes on to explain that findings
from further advanced laboratory analysis suggest that other organisms, including
Entero-aggregative E Coli and Shigella, may also have contributed to the burden of
illness experienced by people who attended the event.
I have enclosed a copy of the Executive Summary of the report with this letter. If you
would like a copy of the full report, it is available on the Newcastle Council website.
I‟d like to thank you for your co-operation with this complex investigation.
Yours sincerely
Dr Kirsty Foster
Consultant in Health Protection / Chair of Outbreak Control Team
Letters sent to cases with positive PCR results
Letter for cases with EAEC and Shigella pcr and salmonella culture +ve results
Dear
Street Spice Festival investigation - Update on results and publication of
outbreak report
I wrote to you in March because you reported illness after visiting the Street Spice
Festival in Newcastle. I am writing to you again to give you an update on the latest
results and to inform you that the outbreak investigation report is being published
today.
As you will be aware, Salmonella was identified by standard laboratory tests in the
stool sample you submitted. However, further testing has identified that you may also
have been infected with two other bacteria - Entero-aggregative E Coli and Shigella.
As you will know from the previous update we sent to people who had reported
illness, we detected an unusual strain of salmonella in samples from human cases
and from a food ingredient used at the event. However, the number of confirmed
salmonella cases we identified was relatively small considering the number of people
reporting symptoms. In addition, many people suffered symptoms for longer than we
typically see with salmonella infection.
The laboratory tests normally undertaken had not detected organisms other than
salmonella, so we arranged for samples to be tested for other organisms using a
new technique, called the polymerase chain reaction or PCR, which is still in
development. At present, this PCR is not part of the standard clinical tests used for
the diagnosis of gastro-intestinal infection so any results have to be interpreted with
caution.
Many of the samples tested using the new technique were positive for Enteroaggregative E Coli and Shigella, both are organisms which are usually associated
with travellers‟ diarrhoea and cause symptoms such as diarrhoea and abdominal
cramp / pain which were similar to the symptoms many people reported in this
outbreak. Affected individuals usually make a full recovery from such infections with
no long term effects.
Your sample was one of these that tested positive which suggests you may also
have been infected with Entero-aggregative E Coli and Shigella. This does not
affect your positive Salmonella result, but suggests that you may have been infected
with three different organisms. It is possible for this to occur and more information is
included in the outbreak report.
We were not able to test food samples from the Festival using these techniques, so
we cannot demonstrate that the Entero-aggregative E.coli or Shigella organisms
were in food at the festival.
The outbreak report which we are publishing today includes a discussion of the
significance of these findings. It concludes that this was a large outbreak of gastro-
Letters sent to cases with positive PCR results
intestinal illness, with Salmonella Agona PT 40 confirmed in 25 cases and also
isolated from a food ingredient used at the event. It goes on to explain that findings
from further advanced laboratory analysis suggest that other organisms, including
Entero-aggregative E Coli and Shigella, may also have contributed to the burden of
illness experienced by people who attended the event.
I have enclosed a copy of the Executive Summary of the report with this letter. If you
would like a copy of the full report, it is available on the Newcastle Council website.
I‟d like to thank you for your co-operation with this complex investigation.
Yours sincerely
Dr Kirsty Foster
Consultant in Health Protection / Chair of Outbreak Control Team