FOOD-BORNE DISEASES
III
FOOD-BORNE DISEASES
CHOLERA
A total of 10 sporadic cases of cholera were reported in 2000 compared with 11 cases
reported in 1999. There were three imported cases; one from Malaysia and two from Indonesia. All
cases were caused by Vibrio cholerae 01, biotype El Tor except for a case caused by V. cholerae
O139. For the El Tor cholera cases, 8 were of serotype Ogawa, and one of serotype Inaba. No
deaths were reported in 2000.
On 26 Mar 2000, a 35-year-old hairdresser was confirmed to be infected with V. cholerae
O139. The case had onset of diarrhoea on 20 Mar 2000 and was admitted to the Communicable
Disease Centre (CDC), Tan Tock Seng Hospital. She had taken “kupang” (green mussels) from a
Malay food stall at her work place during the 5 days prior to her onset of diarrhoea. Five home
contacts and two food handlers screened at CDC were found not to be infected. Samples from the
implicated foodstall were also free from microbial contamination.
The overall incidence rate was 0.3 per 100,000 population with the highest age-specific rate
among the 25-34 year age group. There was no gender difference. (Table 3.1). The morbidity rate
of Malays was 3.5 times higher than that of Chinese (Table 3.2).
Table 3.1
Age-gender distribution and age-specific incidence rates of reported cholera cases in Singapore, 2000
Age group
Male
Female
Total
%
Incidence rates
per 100,000 *
0 – 14
0
0
0
15 – 24
0
1 (1)
1 (1)
10
0
0.2
25 – 34
1
2
3
30
0.5
35 – 44
3 (1)
1
4 (1)
40
0.7
45 – 54
1
0
1
10
0.2
55 – 64
0
0
0
65+
0
1 (1)
1 (1)
10
0.4
5 (1)
5 (2)
10 (3)
100
0.3
Total
0
0
( ) Imported cases included in the total
* Rates are based on 2000 census population
(Source: Department of Statistics, Singapore)
Food-Borne Diseases .................................................... 3 - 1
0
The time and geographical distribution of the reported cases are shown in Figs 3.1 and 3.2,
respectively.
Table 3.2
Ethnic distribution and ethnic-specific incidence rates of reported cholera cases in Singapore,
2000
Ethnic group
No. of Cases
Chinese
Incidence rates
per 100,000*
%
6 (1)
60
Malays
3 (2)
30
Indians
0
0
0
Others
0
0
0
Foreigners
1
10
-
Total
10 (3)
( )
*
0.2
0.7
100
0.3
Imported cases included in the total
Rates are based on 2000 census population
(Source: Department of Statistics, Singapore)
Figure 3.1
Monthly distribution of reported cholera cases in Singapore, 2000
5
Local
Im p o r te d
No . o f c a s e s
4
3
2
1
0
Jan
Feb
M ar
Ap r
M ay
Jun
Jul
Au g
Sep
Oct
No v
Dec
M o n th
CH003/CMH/100401
Food-Borne Diseases .................................................... 3 - 2
Figure 3.2
Geographical distribution of 7 local cholera cases in Singapore, 2000
One case
CH003/CMH/020301
ENTERIC FEVERS
A total of 101 cases of enteric fevers were reported in 2000 compared with 63 cases in 1999,
an increase of 60.3%. Of these, 80 (79.2 %) were typhoid and 21 (20.8 %) were paratyphoid A
(Table 3.3). No deaths were reported.
Table 3.3
Classification of reported enteric fevers cases, 1991-2000
Paratyphoid
Year
Typhoid
Total
A
B
C
1991
109 ( 92)
22 (19)
1 (1)
0
132 (112)
1992
127 ( 98)
30 (19)
5
0
162 (117)
1993
117 (103)
22 (20)
5
0
144 (123)
1994
98 ( 87)
43 (35)
8 (2)
0
149 (124)
1995
110 ( 91)
49 (46)
1 (1)
171 (140)
1996
109 ( 89)
201(29)
5 (1)
1
316 (119)
1997
93 ( 71)
19 (17)
0
0
112 ( 88)
1998
57 ( 44)
22 (15)
1
0
80 ( 59)
1999
48 ( 39)
15 (15)
0
0
63 ( 54)
2000
80 ( 66)
21 (19)
0
0
101 ( 85)
11 (2)
( ) Imported cases included in the total
Food-Borne Diseases .................................................... 3 - 3
Typhoid
Majority of the typhoid cases were imported (82.5 %), mainly from Indonesia (43.9 %) and
India (25.8 %)(Table 3.4).
The overall incidence rate of indigenous typhoid was 0.4 per 100,000 population (Table
3.5). Among the three major ethnic groups, Indians had the highest incidence rate. It was 8 and 5
times higher than that of Malays and Chinese, respectively. (Table 3.6)
Typhoid cases were reported throughout the year (Fig. 3.3) and occurred sporadically throughout the island (Fig. 3.4)
Imported Cases
There was a high incidence of imported typhoid cases in the month of January (Fig. 3.3).
This could be due to more local residents travelling to the endemic countries during the school
holidays in December.
309 imported cases of typhoid were reported during the period 1996-2000 (Table 3.7). Of
these, 110 (35.6 %) were local residents who contracted the disease overseas (Table 3.7), mainly
from Indonesia (55.5%) and India (29.1%) (Table 3.8). The purposes of travel were: social visits
(39.1%), pleasure/vacation (39.1 %) and business/employment (21.8%).
Phage typing
Vi-phage typing was done at the Department of Pathology, SGH for all typhoid cases diagnosed in government and restructured hospitals (except NUH). A total of 27 S. typhi strains were
Vi-phage typed (Table 3.9). The predominant phage type was RDNC.
Paratyphoid
There were 21 reported cases of paratyphoid, of which 19(90.5%) were imported and two
(9.5%) were local cases (Fig. 3.5). The cases were reported throughout the year with more cases
reported in January (Fig. 3.3)
A total of 96 imported cases of paratyphoid were reported during the period 1996-2000. Of
these, 35 (36.5%) were local residents who contracted the disease overseas (Table 3.10), mainly from
Indonesia (48.6%) and India (14.3 %) (Table 3.11). The purposes of travel were: social visits (37.1%),
business or employment (31.4%), pleasure or vacation (28.6 %) and military training (2.9 %).
Food-Borne Diseases .................................................... 3 - 4
Food-Borne Diseases .................................................... 3 - 5
Table 3.4
Imported typhoid and paratyphoid fever cases, 1996-2000
Typhoid
Paratyphoid
Country of origin
1996
1997
1998
1999
2000
Total
1996
1997
1998
1999
2000
Total
Southeast Asia
Malaysia
0
3
3
0
2
8
0
0
1
1
1
3
Indonesia
50
31
24
24
29
158
18
9
6
7
10
50
Philippines
2
2
4
1
3
12
0
0
1
0
0
1
Thailand
1
2
1
0
5
9
0
0
0
0
1
1
Myanmar
1
1
2
1
3
8
3
0
0
0
0
3
Cambodia
0
1
0
1
0
2
0
1
0
1
2
4
Vietnam
1
0
1
0
0
2
0
0
1
0
1
2
Brunei
0
0
0
0
0
0
1
0
0
0
0
1
9
6
3
2
6
26
2
0
3
2
0
7
Indian subcontinent
Bangladesh
India
23
22
4
9
17
75
3
7
0
4
4
18
Pakistan
0
1
1
1
0
3
0
0
0
0
0
0
Nepal
0
1
0
0
1
2
1
0
2
0
0
3
China
2
1
1
0
0
4
1
0
0
0
0
1
Australia
0
0
0
0
0
0
1
0
0
0
0
1
USA
0
0
0
0
0
0
0
0
1
0
0
1
89
71
44
39
66
309
30
17
15
15
19
96
Others
Total
Table 3.5
Age-gender distribution and age-specific incidence rates of indigenous typhoid cases, 2000
Age group
Male
Female
Total
%
Incidence rate
per 100,000*
0-4
3
1
4
28.6
1.9
5 - 14
2
2
4
28.6
0.8
15 - 24
1
1
2
14.3
0.5
25 - 34
2
1
3
21.4
0.5
35 - 44
0
0
0
0
0
45 - 54
0
0
0
0
0
55 - 64
0
1
1
7.1
0.4
65+
0
0
0
0
0
Total
8
6
14
100
0.4
* Rates are based on 2000 census population
(Source: Department of Statistics, Singapore)
Table 3.6
Ethnic distribution and ethnic-specific incidence rates of indigenous typhoid cases, 2000
Cases
%
Incidence rates
per 100,000*
Chinese
7
41.2
0.3
Malays
1
5.9
0.2
Indians
4
23.5
1.6
Others
2
11.8
4.3
Foreigners
3
17.6
-
Total
17
100
0.4
Ethnic group
*Rates are based on 2000 census population
(Source: Department of Statistics, Singapore)
Food-Borne Diseases .................................................... 3 - 6
Figure 3.3
Monthly distribution of reported cases of enteric fevers in
Singapore, 2000
Typhoid
24
22
20
No . o f c a s e s
18
16
14
12
10
8
6
4
2
0
Jan
Feb
Mar
Ap r
May
Jun
Jul
Au g
Sep
Oct
Nov
D ec
Ap r
May
Jun
Jul
Au g
Sep
Oct
N ov
D ec
Paratyphoid
8
7
No . o f c a s e s
6
5
4
3
2
1
0
Jan
Feb
Mar
M o n th
L o c a l c a s e s (fo re ig n e rs )
Im p o rte d c as e s (fo re ig n e rs )
L o c a l c a s e s (lo c a l re s id e n ts )
Im p o rte d c as e s (lo c a l re s id e n ts )
Enteric001/CMH/100401
Food-Borne Diseases .................................................... 3 - 7
Figure 3.4
Geographical distribution of 14 reported indigenous typhoid cases in Singapore, 2000
One sporadic case
Enteric002/CMH/020301
Table 3.7
Classification of imported typhoid cases, 1996-2000
1996
1997
1998
1999
2000
Total
No. (%)
No. (%)
No. (%)
No. (%)
No. (%)
No. (%)
Local residents
37 (41.6)
24 (33.8)
14 (31.8)
14 (35.9)
21 (31.8)
110 (35.6)
Foreigners seeking
medical treatment in
Singapore
20 (22.5)
13 (18.3)
9 (20.5)
6 (15.4)
10 (15.2)
58 (18.8)
Work permit holders
21 (23.6)
23 (32.4)
15 (34.1)
15 (38.5)
16 (24.2)
90 (29.1)
Students pass holders
3 ( 3.4)
5 (7.0)
5 (11.4)
4 (10.3)
15 (22.7)
32 (10.4)
Tourists
8 ( 9.0)
6 (8.5)
1 ( 2.3)
0 (0)
4 ( 6.1)
19 (6.1)
89 (100)
71 (100)
44 (100)
66 (100)
309 (100)
Population group
Total
Food-Borne Diseases .................................................... 3 - 8
39 (100)
Table 3.8
Epidemiological characteristics of local residents who contracted typhoid overseas,
1996-2000
Classification
1996
1997
1998
1999
2000
Total
Indonesia
24
8
11
India
10
9
1
11
7
61
2
10
32
Malaysia
0
2
Thailand
0
2
0
0
1
3
0
0
0
Pakistan
0
2
1
1
1
0
3
China
1
0
1
0
0
2
Country visited
` `
0
1
0
0
0
1
Myanmar
1
0
0
0
3
4
Others
1
1
0
0
0
2
Social visits
15
10
9
5
4
43
Pleasure/vacation
14
8
0
8
13
43
Purpose of travel
Business/employment
8
6
5
1
4
24
Military training
0
0
0
0
0
0
Chinese
14
8
3
5
6
36
Malays
9
3
7
5
4
28
Indians
12
11
1
3
9
36
Others
2
2
3
1
2
10
37
24
14
14
21
110
Ethnic group
Total
Table 3.9
Vi-phage types of S. typhi isolated from reported indigenous and imported typhoid cases, 2000
Countries
A
D2
E1
E2
UVS1
UVS4
RDNC
M1
J1
Total
Bangladesh
0
0
0
0
0
0
2
0
0
2
India
1
0
4
0
0
0
1
0
1
7
Imported
Indonesia
0
1
0
0
1
0
4
0
0
6
Malaysia
0
0
0
0
0
0
1
0
0
1
Philippines
0
0
0
0
0
0
1
0
0
1
Sri-Lanka
0
0
0
0
0
0
1
0
0
1
Thailand
0
0
0
0
0
0
1
0
0
1
Indigenous
1
3
0
0
0
0
4
0
0
8
Total
2
4
4
0
1
0
15
0
1
27
(7.4)
(14.8)
(14.8)
(0)
(3.7)
(0)
(55.6)
(0)
(3.7)
(100)
(%)
Food-Borne Diseases .................................................... 3 - 9
Figure 3.5
Geographical distribution of 2 reported indigenous paratyphoid cases in Singapore, 2000
One case
Enteric002/CMH/150301
Table 3.10
Classification of imported paratyphoid cases, 1996-2000
1996
1997
1998
1999
2000
Total
No. (%)
No. (%)
No. (%)
No. (%)
No. (%)
No. (%)
10 (33.3)
7 (41.2)
5 (33.3)
7 (46.7)
6 (31.6)
35 (36.5)
Foreigners seeking
medical treatment in
Singapore
9 (30.0)
2 (11.8)
4 (26.7)
2 (13.3)
3 (15.8)
20 (20.8)
Work permit holders
5 (16.7)
7 (41.2)
4 (26.7)
5 (33.3)
5 (26.3)
26 (27.1)
Students pass holder
3 (10.0)
1 (5.9)
2 (13.3)
0 (0)
1 (5.3)
7 ( 7.3)
Tourists
3 (10.0)
0 (0)
0 (0)
1 (6.7)
4 (21.1)
8 ( 8.3)
17 (100)
15 (100)
15 (100)
19 (100)
96 ( 100)
Population group
Local residents
Total
30 (100)
Food-Borne Diseases .................................................... 3 - 10
Table 3.11
Epidemiological characteristics of local residents who contracted paratyphoid overseas,
1996-2000
Classification
1996
1997
1998
1999
2000
Total
%
Indonesia
6
5
1
3
2
17
48.6
India
1
2
0
1
1
5
14.3
Malaysia
0
0
1
1
1
3
8.5
Thailand
0
0
0
0
1
1
2.9
Country visited
Myanmar
1
0
0
0
0
1
2.9
China
1
0
0
0
0
1
2.9
Nepal
0
0
1
0
0
1
2.9
Bangladesh
0
0
1
1
0
2
5.7
USA
0
0
1
0
0
1
2.9
Cambodia
0
0
0
1
1
2
5.7
Others
1
0
0
0
0
1
2.9
Social visits
4
4
2
2
1
13
37.1
Pleasure/vacation
2
2
1
1
4
10
28.6
Purposes of travel
Business/employment
4
1
2
4
0
11
31.4
Military training
0
0
0
0
1
1
2.9
Chinese
3
2
4
2
4
15
42.9
Malays
4
3
1
2
1
11
31.4
Indians
2
2
0
2
0
6
17.1
Others
1
0
0
1
1
3
8.6
10
7
5
7
6
35
Ethnic group
Total
100
Enteric fevers carrier registry
No carrier was picked up in 2000. Since 1974, a total of 194 typhoid and nine paratyphoid
carriers were notified (Table 3.12). The overall carrier rate was 6.2 per 100,000 population with the
highest age-specific carrier rate in the 55-64 years age group (Table 3.13). The male to female
ratio was 1.3:1. The carrier rate among Indians was 1.4 times higher than that of Chinese and 1.2
times that of Malays (Table 3.14). Food handlers comprised 14.4% of all the carriers detected
since 1974. The majority (90.5%) were stool carriers (Table 3.15).
Food-Borne Diseases .................................................... 3 - 11
Table 3.12
Typhoid and paratyphoid carriers detected in Singapore, 1974-2000
Typhoid
Paratyphoid
Year
Chronic
Convalescent Temporary Total
1974-89
14
40
86
140
1990
0
0
48
1991
0
0
0
1992
1
0
1993
0
0
1994
0
1995
1996
Chronic Convalescent Temporary
Total
1 (B)
3 (A)
5 (4A)
(1C)
9 (7A)
(1B)
(1C)
48
0
0
0
0
0
0
0
0
0
0
1
0
0
0
0
0
0
0
0
0
0
0
1
1
0
0
0
0
1
0
0
1
0
0
0
0
2
0
0
2
0
0
0
0
1997
1
0
0
1
0
0
0
0
1998
0
0
0
0
0
0
0
0
1999
0
0
0
0
0
0
0
0
2000
0
0
0
0
0
0
0
0
Total
19
40
135
194
1 (B)
3 (A)
5 (4A)
(1C)
9 (7A)
(1B)
(1C)
Table 3.13
Age-sex distribution and age-specific typhoid and paratyphoid carriers rates in Singapore,
1974-2000
Typhoid and paratyphoid carriers
Carrier rates
Age group
Male
Female
Total
Per 100,000*
0-4
0
0
0
0
5-14
5
2
7
1.4
15-24
10
9
19
4.5
25-34
35
20
55
9.8
35-44
21
14
35
5.5
45-54
26
15
41
8.7
55-64
17
22
39
16.5
65+
1
6
7
2.9
Total
115
88
203
6.2
*Rates are based on 2000 census population
(Source: Department of Statistics, Singapore)
Food-Borne Diseases .................................................... 3 - 12
Table 3.14
Ethnic-specific typhoid and paratyphoid carrier rates in Singapore,1974-2000
Typhoid and
paratyphoid carriers
Carrier rates
per 100,000*
Chinese
137
5.5
Malays
30
6.6
Indians
19
7.4
Others
9
19.4
Foreigners
8
-
Total
203
6.2
Ethnic group
*Rates are based on 2000 census population
(Source: Department of Statistics, Singapore)
Table 3.15
Distribution of typhoid and paratyphoid carriers in Singapore by occupation and type of excretors,
1974-2000
Occupation
Type of excretors
Year
Food Handler
Others
Stool
Urine
Bile
1974-1989
29
120
131
8
10
1990
0
48
48
0
0
1991
0
0
0
0
0
1992
0
1
1
0
0
1993
0
0
0
0
0
1994
0
0
0
0
0
1995
0
1
1
0
0
1996
0
2
1
0
1
1997
0
1
1
0
0
1998
0
0
0
0
0
1999
0
0
0
0
0
2000
0
0
0
0
0
Food-Borne Diseases .................................................... 3 - 13
SHIGELLOSIS
A total of 7 sporadic cases of shigellosis caused by Shigella flexneri (57 %) and Shigella
sonnei (43 %) were reported in 2000. All Shigella isolates were from stool specimens. The agegender distribution and age-specific incidence rates are shown in Table 3.16. The male to female
ratio was 6:1. Among the three major ethnic groups, the incidence rate of Malays was 4 times that
of Chinese. (Table 3.17). No deaths were reported.
Table 3.16
Age-gender distribution and age-specific incidence rates of reported shigellosis in Singapore, 2000
Age Group
Male
Female
Total
%
Incidence rates
per 100,000*
0-4
1
0
1
14.3
0.5
5-9
2
1
3
42.9
1.2
10-14
1
0
1
14.3
0.4
15-24
1
0
1
14.3
0.2
25-34
1
0
1
14.3
0.2
35-44
0
0
0
0
0
45-54
0
0
0
0
0
55-64
0
0
0
0
0
65+
0
0
0
0
0
Total
6
1
7
100
0.2
*Rates are based on 2000 census population
(Source: Department of Statistics, Singapore)
Table 3.17
Ethnic distribution and ethnic-specific incidence rates of reported shigellosis in Singapore,
2000
Cases
%
Incidence rates
per 100,000*
Chinese
3
42.9
0.1
Malays
2
28.6
0.4
Indians
0
0
0
Ethnic group
Others
1
14.3
2.2
Foreigners
1
14.3
-
Total
7
100
0.2
*Rates are based on 2000 census population
(Source: Department of Statistics, Singapore)
Food-Borne Diseases .................................................... 3 - 14
SALMONELLOSIS
A total of 85 sporadic cases of salmonellosis caused by Salmonella enteritidis were reported
(Table 3.18). The incidence rate was highest in children below five years of age. Among the three
major ethnic groups, the incidence rate was highest among the Malays (Table 3.19).
Table 3.18
Age-gender distribution and age-specific incidence rates of reported Salmonella enteritidis in
Singapore, 2000
Age group
Male
Female
Both (%)
Incidence rates
per 100,000*
0-4
16
21
37 (43.5)
17.3
5 - 14
5
3
8 (9.4)
1.7
15 - 24
1
0
1 (1.2)
0.2
25 - 34
7
5
12 (14.1)
2.1
35 - 44
7
2
9 (10.6)
1.4
45 - 54
3
3
6 (7.1)
1.3
55 +
8
4
12 (14.1)
9.6
Total
47
38
85 (100)
2.6
*Rates are based on 2000 census population
(Source: Department of Statistics, Singapore)
Table 3.19
Ethnic distribution and ethnic-specific incidence rates of reported
Salmonella enteritidis in Singapore, 2000
Cases (%)
Incidence rates per
100,000*
Chinese
55 (64.7)
2.2
Malays
17 (20.0)
3.7
Indians
5 (5.9)
1.9
Others
1 (1.2)
2.2
Foreigners
7 (8.2)
-
Total
85 (100)
Ethnic group
*Rates are based on 2000 census population
(Source: Department of Statistics, Singapore)
Food-Borne Diseases .................................................... 3 - 15
2.6
Outbreak of multi-drug resistant Salmonella typhimurium
In July 2000, an unusual increase in the isolation of S. typhimurium definite type 104 (DT104)
or phage type 104 (PT104) with resistance to ampicillin, chloramphenicol, gentamicin, streptomycin, tetracycline and sulphonamide or R-type ACGSTS3), was noted by the Department of Pathology, Singapore General Hospital. The isolates came mainly from the stool cultures of children
below 18 months of age.
The Quarantine & Epidemiology Department of the Ministry of the Environment was notified
and epidemiological investigations were conducted.
Epidemiological investigations
Infants and toddlers aged between one month and 36 months whose stool cultures were
positive for S. typhimurium DT104L during the period July-August 2000 were traced to determine
the source of infection and the mode of transmission. The home of each child was visited to look
for other unreported cases among contacts. The parent, guardian, or domestic maid was interviewed by two trained environmental health officers using a structured questionnaire. Over 90
questions were included to elicit clinical and epidemiological information such as intake of different food items, food handling and personal hygiene practices in the kitchen and contact with
household pets with diarrhoea. For each notified case, 2-3 controls comprising children of the
same age group (within 6 months of the age of the case), gender and ethnic group living in the
same neighbourhood, and with no recent travel history and gastro-intestinal symptoms during the
previous 2 weeks, were selected and interviewed. The questionnaire covered 3 days preceding
the onset of symptoms of the cases, and for the controls, 3 days preceding the interview.
Samples of milk powder, cereal and other food items were obtained from the homes of the
cases and retail outlets, and submitted to the Food and Water Laboratory, Singapore General
Hospital, for isolation of Salmonella species.
Differences in proportion between cases and controls were examined using chi-square or
Fisher’s exact test; a p-value of <0.05 was considered to be statistically significant.
Results
During the period 13 July – 17 October 2000, a total of 33 isolates of S. typhimurium of the
same R-type ACGSTS3 and of the same phage type 104L were identified. Their PFGE patterns
were indistinguishable. Of the isolates, 17 were detected in July, 10 in August, 4 in September and
2 in October. Except for 4 adults aged between 31 years and 66 years, all the others were toddlers
and infants as young as 2 days of age. There were 19 males and 14 females (Table 3.20). None
Food-Borne Diseases .................................................... 3 - 16
Table 3.20
Age-gender distribution of 33 reported cases of S. typhimurium phage type 104L, Singapore
Age group
Male
Female
Total
<6 months
4
2
6
6 months – 11 months
6
4
10
1 year
3
4
7
2 years
3
0
3
3 years
1
0
1
4 years
0
0
0
5 – 14 years
0
2
2
15 – 24 years
0
0
0
25 – 34 years
0
1
1
35 – 44 years
0
1
1
55+ years
2
0
2
19
14
33
TOTAL
of them had a recent travel history outside Singapore. All the cases occurred singly and sporadically and were not clustered in any particular locality. No secondary cases were identified in the
same household.
The main presenting clinical symptoms of 19 cases investigated were watery diarrhoea
(100%), fever (78.9%), vomiting (52.6%) and abdominal cramps (26.3%). About 58% had bloody
stool. Seventeen of them were hospitalised and 2 were treated as outpatients. No death was
reported.
Results of the case-control study based on 19 cases and 55 controls implicated porridge
with “ikan bilis” (dried anchovy) as the vehicle of transmission (p<0.01). No other food items or risk
factors were incriminated (Table 3.21).
None of the food samples taken from the homes of 6 cases, including one sample of grounded
dried anchovy, were positive for Salmonella species. Salmonella group E was isolated from one
of the 16 samples of dried anchovies subsequently purchased from the retail outlets. However,
further samples collected were repeatedly free from Salmonella contamination.
Food-Borne Diseases .................................................... 3 - 17
Table 3.21
Results of matched case-control analysis in an outbreak of Salmonella typhimurium PT104L,
Jul to Oct 2000
Cases
(n=19)
Controls
(n=55)
Uncooked
0/19
1/55
-
Partially cooked
4/19
12/55
Cooked
3/19
23/55
Powdered milk formula
18/19
Pasteurised milk
1/19
Reconstituted/UHT milk
95%CI
p-value
-
0.74
0.96
0.27-3.42
0.94
0.26
0.07-1.00
0.04
48/55
2.63
0.30-22.86
0.37
6/55
0.45
0.05-4.03
0.47
0/19
1/55
-
-
0.74
Cereals with milk
8/19
21/55
1.18
0.41-3.40
0.76
Baby food
1/19
1/55
3.00
0.18-50.47
0.43
0.97-8.69
0.05
-
0.30
Food items/risk factors
OR
Egg
Dairy products
Cheese
9/19
13/55
2.91
Yoghurt
0/19
4/55
-
“Yakult”
2/19
12/55
0.42
0.09-2.09
0.28
“Vitagen”
2/19
9/55
0.60
0.12-3.07
0.54
Alone
6/19
10/55
2.08
0.64-6.80
0.22
With chicken
4/19
26/55
0.30
0.09-1.01
0.05
With pork
7/19
29/55
0.52
0.18-1.53
0.23
With beef
0/19
4/55
-
-
0.30
Porridge
With liver
1/19
6/55
0.45
0.05-4.03
0.47
14/19
14/55
8.2
2.5-26.9
0.0001
With supplements
0/19
1/55
-
-
0.74
Without supplements
0/19
4/55
-
-
0.30
Fruits
11/19
21/55
2.23
0.77-6.43
0.14
Fruit juices
4/19
11/55
1.07
0.30-3.86
0.92
Raw vegetables
0/19
2/55
-
-
0.98
Animal contact
0/19
3/55
-
-
0.57
Household contact with diarrhoea
0/19
5/55
-
-
0.24
Handwashing before preparing food
13/19
51/55
0.17
0.04-0.69
0.02
Storage of “ikan bilis” in chiller
4/19
10/55
1.2
0.33-4.40
0.78
With “ikan billis” (dried anchovy)
Breast fed
Food-Borne Diseases .................................................... 3 - 18
Comments
This outbreak of S. typhimurium DT104L was associated with the consumption of grounded
“ikan bilis” (dried anchovies). However, the same strain was not detected from samples taken
from the retail outlets, although another serogroup (Salmonella group E) was detected.
The “ikan bilis” was imported from Thailand, Vietnam, Malaysia and Indonesia and sold at
retail outlets throughout the country. The small anchovies caught in fishing villages in these countries were lightly salted and dried outdoor. This method of processing “ikan bilis” is subject to
gross environmental contamination, including excreta of birds, rats and flies. After processing, the
dried seafood was packed in gunny sacks and exported. It was transported by container trucks,
fishing boats or lorries to Singapore. Further contamination could have occurred during transport,
storage and display at retail outlets where it was usually sold without proper packing and labelling.
The dried anchovy is a rich source of calcium and protein and is a popular ingredient for the
preparation of a variety of foods, including soup stock. It is commonly deep fried and served with
chilli. If used as an infant feed, the common practice is to grind it and then cooked with porridge.
In this outbreak, it was found that in the households where cases had occurred, the “ikan bilis” was
first ground and stored in a container at room temperature for subsequent use. It was either
sprinkled onto or added to freshly cooked porridge, instead of boiling with the porridge, and served.
This is an isolated incident believed to be due to a batch of contaminated “ikan bilis” imported into the country. The dried anchovy should be thoroughly cooked before consumption.
The practice of sprinkling or adding ground “ikan bilis” onto cooked porridge should be discouraged as the temperature attained would not be adequate to destroy the Salmonella present in the
food.
FOOD POISONING
A total of 213 notifications involving 1,542 cases were reported in 2000, compared with 170
notifications involving 1,044 cases in 1999, an increase of 47.7 % in the number of reported cases
(Fig 3.6). 136 of these notifications were classified as outbreaks as in each of the episodes, two or
more cases were traced to a common source. Twenty-seven of the outbreaks involved ten or more
persons.
Majority of the outbreaks (66.9%) occurred in restaurants and eating houses (Table 3.22).
Contributing factors such as poor environmental hygiene were identified in 16 (11.8%), and
poor personal and food hygiene in 42 (30.9%) of the 136 outbreaks (Table 3.23).
Food-Borne Diseases .................................................... 3 - 19
Figure 3.6
Notification of food poisoning in Singapore, 1965 - 2000
220
2000
Cases
1800
200
No tific a tio n s
180
1600
160
1400
Cases
120
1000
100
800
No tific a tio n s
140
1200
80
600
60
400
40
200
20
0
0
65
67
69
71
73
75
77
79
81
83
85
87
89
91
93
95
97
99
Year
FP001/CMH/100401
Table 3.22
Food poisoning notifications by type of food establishment, 2000
Type of food establishments
No. of notifications
No. of cases
Restaurant
In hotels
27 (21)
265
Others
53 (41)
251
60 (29)
172
4 ( 3)
15
Eating house
Hawker centre
ENV
HDB
Private food court
4 ( 2)
7
19 (12)
41
Fast food outlets
8 ( 4)
15
Other food outlets
13 ( 4)
21
Canteens
Factory/office/staff/construction site
2 ( 1)
34
School
11 (10)
217
Tertiary
1 ( 0)
1
2 ( 1)
4
Catering (licensed)
1 ( 1)
20
In house kitchen (police)
1 ( 1)
5
Others
7 ( 6)
474
213 (136)
1,542
arket/market shops
Total
( ) Indicates number of outbreaks
Food-Borne Diseases .................................................... 3 - 20
Table 3.23
Contributing factors identified during epidemiological investigations
of 136 food poisoning outbreaks, 2000
No. of
outbreaks
%
42
30.9
(a) Food sample contaminated with human pathogen
24
17.6
(b) Dirty finger nail
1
0.7
(c) Double stacking of cooked food
1
0.7
(d) Exposing cooked food without cover
4
2.9
(e) Improper storage of cooked and raw food
9
6.6
(f) Using bare hands to handle cooked food
2
1.4
(g) Unclean article in contact with food
1
0.7
16
11.8
(a) Cockroach infestation in premises
3
2.2
(b) Dirty premises
3
2.2
(c) Dirty chopping board
5
3.7
(d) Dirty storage cabinet
2
1.4
(e) Dirty coldroom
3
2.2
Contributing factors
(1) Poor personal and food hygiene
(2) Poor environmental hygiene
A total of 376 food samples were taken during epidemiological investigations. Eleven were
positive for Escherichia coli; six were positive for Staphylococcus aureus; four were positive for
Vibrio parahaemolyticus; two were positive for Salmonella organisms and one was positive for
mould. Of the 298 implicated food handlers sent for screening at the Communicable Disease
Centre, four were found positive for Vibrio parahaemolyticus; three were found positive for
Aeromonas species; two positive for Salmonella organisms; one positive for Vibrio fluvialis and
one positive for Campylobacter species.
A food poisoning outbreak in a secondary school
On 2 Mar 2000, the vice-principal of a secondary school notified the Quarantine & Epidemiology Department, Ministry of the Environment, of an outbreak of food poisoning which affected
several students who had attended a cross-country run on Friday, 25 Feb 2000. The outbreak was
first recognised when the vice-principal received feedback that a number of students who were
absent from school on 28 and 29 Feb had been ill with vomiting and diarrhoea, and one of them
was admitted to Singapore General Hospital.
Food-Borne Diseases .................................................... 3 - 21
Epidemiological investigations
As soon as the notification was received, epidemiological investigation was conducted to
determine the source of infection and the mode of transmission.
It was found that more than 1,200 students and staff took part in the cross-country run from
8.30am to 11.00am at the MacRitchie reservoir. The students were provided with light refreshment
which consisted of chilled beverage (provided by a beverage company) and iced water (prepared
by a group of girl guides).
Case-control study was undertaken to determine the vehicle of transmission. A set of questionnaires was prepared to elicit information on the food items consumed up to 72 hours prior to
onset of illness, as well as clinical signs and symptoms. The questionnaires were administered to
a random sample of both ill and well students after careful explanation. Site visits were made to the
school canteen, MacRitchie reservoir where the iced water was prepared and served, and the ice
factory. Food, water, ice and environmental samples were collected and sent to the Food and
Water Laboratory, Singapore General Hospital, for bacteriological analyses. The food handlers
from the beverage company and the girl guides who prepared the iced water were referred to the
Communicable Disease Centre for screening of enteropathogens.
Results
A total of 269 students came down with food poisoning. The main clinical symptoms were
abdominal cramps (68.0%), diarrhoea (60.6%), vomiting (59.5%), fever (54.3%), headache (52.4%)
and nausea (31.6%). The onset of symptoms for the first case was on 25 Feb 2000 at 10.00 am
and the last case on 27 Feb 2000 at 11.30 pm (Fig. 3.7).
Based on the analysis of food-specific attack rates of 55 cases and 175 control subjects,
consumption of iced water and chilled beverage was found to be statistically significantly associated with the illness (p<0.001 and p<0.05, respectively) (Table 3.24). Stratified analyses showed
that cases were more likely to have taken the iced water after controlling for the consumption of
chilled beverage (Mantel-Haenszel weighted odds ratio = 18.4, 95% CI = 6.9 - 48.9; p<10-6). The
mean and median incubation periods, based on the interval between consumption of iced water
and onset of illness, were 28.7 hours and 29.7 hours, respectively.
A sample of block ice taken from the ice factory on 2 Mar was tested positive for Staphylo-
coccus aureus. E. coli was detected in environmental swabs taken from the wash area near the
public toilet at MacRitchie reservoir where the iced water was prepared, and from one of the
containers that was used to hold the iced water. The swab taken from another container was
positive for both Staphylococcus aureus and E. coli. All the food handlers of the beverage com-
Food-Borne Diseases .................................................... 3 - 22
Figure 3.7
Onset of illness for 269 cases of food poisoning at a school cross-country event,
25 - 27 February 2000
45
40
35
N o. of cases
30
25
20
15
10
5
0
00
0:
0
:0
21
0
:0
18
0
:0
15
00
:0
00
26 February
12
9:
00
6:
3:
0
00
0:
0
21
:0
0
18
:0
0
:0
15
:0
00
25 February
12
00
00
9:
6:
3:
0
00
0:
0
:0
21
0
18
:0
0
:0
15
00
:0
12
00
9:
00
6:
3:
0:
00
0
27 February
T ime o f onset
FP001/CMH/240300
Table 3.24
Analysis of food - specific attack rates in the food poisoning outbreak at a school cross country event
Case patients
Control subjects
Food items*
P value
Ate
Steamed bun
"Roti prata"
Did not eat
% ate
Ate
Did not eat
% ate
3
52
5.5
8
167
4.6
ns
ns
11
44
20.0
25
150
14.3
Curry chicken
0
55
0
4
171
2.3
ns
Mixed vegetables
2
53
3.6
3
172
1.7
ns
Fried "kway teow"
0
55
0
3
172
1.7
ns
Egg
2
53
3.6
4
171
2.3
ns
"Tao pok"
3
52
5.5
0
175
0
ns
Cooked pork
2
53
3.6
4
171
2.3
ns
"Wanton" noodles
5
50
9.1
23
152
13.1
ns
"Laksa"
2
53
3.6
0
175
0
ns
Chicken noodles
1
54
1.8
0
175
0
ns
Prawn noodles
0
55
0
0
175
0
ns
Ipoh "hor fun"
0
55
0
1
174
0.6
ns
"Nasi lemak"
2
53
3.6
7
168
4.2
ns
"Sambal" egg
1
54
1.8
3
172
1.7
ns
Sausage
1
54
1.8
4
171
2.3
ns
Cut water melon
5
50
9.1
4
171
2.3
ns
Soya bean drink
8
47
14.5
19
156
10.9
ns
Chilled beverage
52
3
94.5
147
28
84.0
<0.05
Iced water
52
3
94.5
84
91
48.0
<0.0001
* List does not include 105 other food items which were not statistically significantly associated with the illness
ns = not statistically significant at p<0.05
Food-Borne Diseases .................................................... 3 - 23
pany and the girl guides involved in preparation of the iced water were negative for enteropathogens.
Samples taken of tap water and chilled beverage were found to be free from contamination.
Further investigations were conducted to determine the chain of events that led to the implicated food being contaminated, from the time of production of the ice in the factory to distribution
of the iced water. The factory had separate facilities and production lines for food-grade and nonfood-grade (industrial) ice. Both types of ice were produced using potable water. For food-grade
ice, the water went through filtration followed by ozonisation. The water then passed into an icemaking machine that churned out ice cubes or, after compression, tube ice. These were then
transported by an automatic conveyor system to the packaging site and bagged. Manual handling
was not involved in the whole process.
For non-food-grade ice, the water was filtered and passed into large metal containers without ozonisation. The containers were then lowered into the floor slots, covered over with wooden
planks and frozen into ice blocks. The ice blocks were washed, dragged on the floor to the metal
saw and cut into the required size. Environmental contamination was observed to occur at various
stages of the production process.
For the cross-country event, the school had actually ordered food-grade ice cubes a few days
in advance. However, the factory mistakenly delivered 8 bags of non-food-grade ice blocks in a
refrigerated truck to the MacRitchie reservoir site on 25 Feb at 7.15 am. The ice blocks in plastic
bags were broken into smaller pieces by dropping them on the floor. The ice was then handled with
bare hands and placed into the drink containers filled with potable water taken from the tap in front of
the public toilet. The girl guides subsequently filled up the cups with the iced water and placed them
at the drinking stations for distribution to the runners from 9.00 am to 11.00 am.
Comments
This is a common source foodborne outbreak traced to the consumption of contaminated
iced drink made from non-food-grade ice. The presence of Staphylococcus aureus in a sample of
block ice as well as the detection of both Staphylococcus aureus and Escherichia coli in the water
container, indicated that contamination could have occurred both in the factory and during preparation of the iced drinks.
The epidemiological and clinical features of this outbreak suggested two aetiologies. A small
cluster of cases with a short incubation period of about 6 hours and clinical symptoms of abdominal cramps and vomiting indicated ingestion of an enterotoxin. A larger cluster of cases who had a
longer incubation period, and with main clinical features of fever, vomiting and diarrhoea indicated
infection by an enteric pathogen.
Food-Borne Diseases .................................................... 3 - 24
The Ministry of the Environment has further tightened its control over the production and sale
of food-grade ice. Ice for consumption is required to be properly packed and labelled to indicate its
intended use. This will enable consumers to distinguish food-grade ice from non-food-grade ice
which is used for chilling seafood and for other industrial purposes. Food handlers should also
observe good personal and food hygiene by preparing iced drinks in a clean and hygienic environment. Gloves should be worn or a clean implement used when ice is handled. Ice factories are
cautioned to refrain from supplying non-food-grade ice blocks to food establishments. Food outlets
are also periodically checked to ensure that only food-grade ice is used for consumption.
A water-borne outbreak of gastroenteritis
On Friday, 18 August 2000, at 4:30 pm, the Quarantine and Epidemiology Department of the
Ministry of the Environment was notified by a general practitioner who noted an unusual increase
of acute gastroenteritis cases seen in his clinic at Bukit Timah Plaza.
The Plaza is an office/shopping/residential complex built more than 25 years ago. It comprises 269 apartments, one 30 storeys and the other 13 storeys located above a 6-storey podium
which has 188 units of shops and offices and a food court.
Epidemiological Investigation
As soon as the notification was received, officers from the Quarantine & Epidemiology Department, Ministry of the Environment went down to the Plaza to investigate. The doctor reported
that he had seen 24 patients with symptoms of acute gastroenteritis on 17 and 18 August. He
noted that the cases were mostly residents or workers at the building. He suspected that contaminated water supply could be the cause of the illness as one of his nurses came down with gastroenteritis after consuming unboiled tap water at the clinic. He also suffered similar symptoms although he did not drink any water taken directly from the tap. He further observed that the sewage
system in his clinic had been periodically choked; the last incident occurred on 16 August 2000.
Epidemiological investigation was conducted to determine the source of infection and the
mode of transmission. The particulars of the reported cases were obtained from the clinic. The
patients were interviewed regarding the food history up to 3 days prior to their onset of illness.
Special attention was given to the consumption of unboiled water taken directly from the tap.
Contact tracing was also carried out to look for other unreported cases. Other clinics in the building
and in the vicinity were contacted to find out whether or not there had been an increase in gastroenteritis cases.
The plan of the water distribution system was obtained from the management corporation,
and water samples were randomly collected from the taps of the clinic, apartments of reported
Food-Borne Diseases .................................................... 3 - 25
cases, shopping centre, food court, swimming pool, and water tanks for testing of faecal coliform,
Escherichia coli and other enteropathogens. Foodhandlers of the implicated foodstalls at the food
court were screened for food poisoning bacteria. Stool and vomitus samples obtained from the
patients at the clinics were sent to the Department of Pathology, Singapore General Hospital, for
laboratory analyses.
Results
A total of 122 cases of gastroenteritis with onset of illness from 13 August to 23 August 2000
were reported (Fig. 3.8). The main clinical symptoms were diarrhoea (90.5%) and vomiting (40%).
Four of them were hospitalized. The cases comprised 49 (40.1%) residents in the apartments and
73 (59.8%) office workers in the building. The median age was 30 years (range 1 - 74 years).
About 65% of the cases were females.
On 22 August, a water sample taken from the doctor’s clinic was found to be positive for
faecal coliform and Escherichia coli. On the same day, stool samples collected from 2 hospitalised
children were found to be positive for rotavirus. Engineers from the Sewage Department and
Public Utilities Board (PUB) were immediately alerted and joint inspections were conducted with
Environmental Health Officers to trace the source of faecal contamination of the water supply
system.
Figure 3.8
Onset of illness in the water-borne outbreak of gastroenteritis at Bukit Timah Plaza,
August 2000
18
16
Faecal coliform and E coli detected
and water supply shut off;
water tanks and piping system
flushed and disinfected
Notification
Chokage of
sanitary
plumbing line
in clinic
14
12
No . o f c a s e s
Water supply restored
10
8
6
4
2
0
12
13
14
15
16
17
18
19
20
D a te o f o n s e t
Food-Borne Diseases .................................................... 3 - 26
21
22
23
24
25
26
Investigation showed that at the basement level were 2 water tanks which received water
directly from the PUB water mains. From these basement tanks, the water was distributed to the
whole shopping/office/residential complex. Running across the top of the water tanks were 3 sanitary plumbing lines each encased by an aluminum tray to prevent any sewage leakage from contaminating the tanks (Fig. 3.9).
The sanitary plumbing lines were old and badly maintained. Some portions were corroded
and clogged. One section above the water tanks was leaking. A metal manhole cover for sealing
one of the water tanks was also missing. In addition, some of the bolts and nuts which were used
to fasten the metal plates of the top of the water tank were also missing. This allowed the sewage
that had dripped from the pipe and pooled on top of the tank to flow into it, thus causing the faecal
contamination.
Management of the outbreak
An operations room was set up in the Management Corporation’s office on 22 August. The
main water supply was cut off immediately. All residents and workers in the offices were advised to
boil the water and to seek medical attention if they had symptoms of gastroenteritis. The food court
and the swimming pool were also closed down. The occupants of the complex was provided with
potable water distributed by PUB water tankers.
Figure 3.9
Sketch of sewage pipes above the basement tanks
Waste water from wash basins and WCs of Medical Centre and Health Centre
50mm diameter
cast Iron waste pipe
Pondin
g of w
aste w
ater
Missing cover
Floor above low level tank
50mm diameter
cast Iron waste pipe
100mm diameter cast iron waste pipe
(about 300mm above top of tank)
Food-Borne Diseases .................................................... 3 - 27
Other0010/CMH/160501
The basement water tanks were disinfected and protected from further sewage contamination. The clogged sanitary plumbing line was flushed and the corroded part replaced. The missing
manhole cover for the water tank was replaced.
The water supply was finally restored at midnight on 23 August when bacteriological analyses of water samples collected from all parts of the complex were found to be repeatedly negative
for faecal coliforms.
Comments
Clustering of cases of gastroenteritis in the office/shopping/residential complex pointed to
two possible sources of infection: contaminated food or contaminated water. Preliminary epidemiological investigation did not suggest a water-borne outbreak, as careful enquiries showed that
those who only consumed boiled water, especially infants and toddlers, also came down with
gastroenteritis. Initial inspection of the water distribution system did not reveal any leakage in the
sanitary plumbing line above the water tanks in the poorly lit basement. This could be due to lack
of experience of the investigating officers.
Prior to 1982, there was no specific code of practice, which prohibited sanitary plumbing line
from running over water tanks. However, the management corporation is required to regularly
maintain and clean the water tanks, submit water samples regularly for bacteriological testing and
report the findings to the PUB. In this outbreak, the management corporation had conducted its
routine checks in July 1999. The licensed plumber appointed by the management corporation had
notified the PUB on 12 August that the water tanks were scheduled for cleaning on 18 August but
this was not carried out.
To prevent similar incidents from occurring, a total of 296 commercial buildings and private
apartments that are more than 20 years old were checked. 19 buildings were found to have sewage pipes positioned over the water tanks. One of them was found to have corroded pipes. The
rest were in good condition and well maintained. In these buildings, either the sewage pipe or
water tank was relocated to prevent contamination of water supply.
This outbreak illustrates the integral role of medical practitioners in the disease surveillance
system. By practising a high level of vigilance for any unusual occurrences, they can take urgent
action to notify the health authorities.
An outbreak of ciguatera fish poisoning
Two suspected cases of ciguatera fish poisoning were notified to the Ministry of the Environment (ENV) by an infectious disease physician in private practice on 27 April 2000.
Food-Borne Diseases .................................................... 3 - 28
Investigation showed that both cases had consumed blue mussels, a pan-fried fish called
“Kawa-kawa” and clam chowder from an upmarket seafood restaurant on 22 April 2000 at 1.30pm.
About seven hours later, they developed diarrhoea, vomiting, myalgia, headache, numbness of
the lower limbs, lack of motor co-ordination, and lethargy. The blood pressure of one of them seen
at the Accident and Emergency Department, Singapore General Hospital, at around midnight on
22 April 2000 was found to be abnormally low. No other obvious clinical signs were detected on
clinical examination. On 23 April 2000, both cases developed pruritis, reversal of hot and cold
sensation and insomnia.
The implicated “Kawa-kawa” fish (mackerel) was imported by a company licensed by the
Agri-Food Veterinary Authority of Singapore (AVA), from a fresh seafood processing plant in Fiji.
The plant possessed a document which certified that it fully complied with the requirements set by
the US Food and Drug Administration. A total of 164 kg (3 cartons) of frozen fish fillets, derived
from different types of coral fish, were air-freighted to Singapore on 1 March 2000.
As soon as notification was received, AVA and ENV ordered the importer to stop the sale of
Fijian fishes and to cancel further import of such fishes. The remaining stocks from the implicated
restaurant and three hotels were recalled by AVA.
Results of analyses of fish fillets obtained from the implicated restaurant using the ELISA
method showed two samples to be weakly positive, but these were subsequently found to be
negative by mouse bioassay. Further tests are being carried out by AVA.
Further investigation by AVA revealed that the importer had wrongly declared Australia as
the exporting country in the TradeNet system. The frozen fillets were therefore not subjected to
routine testing for ciguatoxin, as Australian fish is not prone to be contaminated with this toxin.
AVA will continue to ban the importation of marine products from ciguratera-endemic regions.
Comments
Ciguatera fish poisoning (CFP) is caused by certain species of tropical or subtropical coral
reef-associated fish that consumes several species of toxic dinoflagellates (algae). The algae
species most often associated with CFP is Gambierdiscus toxicus. In Hawaii and throughout the
Central Pacific, barracuda, mackerel, amberjack and snapper are frequently ciguatoxic, and many
other species, both large and small, are suspect.
There are at least 4 known ciguatera toxins that concentrate in the viscera, head or central
nervous system of affected fish. The toxin is tasteless and heat-stable. Cooking does not render
the fish safe for consumption.
Food-Borne Diseases .................................................... 3 - 29
The symptoms of CFP can be classified into three categories; namely, neurological [paresthesia in the perioral area or the extremities, myalgia, arthralgia, dizziness, headache and dysesthesia (reversal of hot and cold sensation)]; gastrointestinal (nausea, vomiting, abdominal pain
and diarrhoea); and cardiovascular (low blood pressure, bradycardia or tachycardia)]. In severe
cases, complications may result in respiratory arrest, convulsion and coma. The symptoms, which
usually begin 2 - 5 hours after ingestion of the toxic fish, may last for a week or so in mild cases, but
may persist for several months or longer in some cases. There is no specific treatment; only
symptomatic and supportive care.
The clinical diagnosis of CFP in these two cases was based on the characteristic combination
of gastrointestinal and neurological symptoms and recent history of consumption of a coral fish
imported from an area where this biotoxin is known to occur. However, the diagnosis could not be
confirmed by detection of ciguatoxin in the implicated fish. This could be because the occurrence of
toxic fish is sporadic and not all fish of a given species or from a given locality will be toxic.
This incident of CFP is the first to be reported in Singapore, although there could be cases in
the past that had not been suspected clinically.
DIARRHOEAL DISEASE SURVEILLANCE
Outpatient attendances for diarrhoeal illnesses remained well below the epidemic threshold
level except in the month of January and February (Figure 3.10).
Figure 3.10
Diarrhoeal disease surveillance in government polyclinics, 2000
1600
1400
Epidemic threshold
No. of a ttendances
1200
1000
800
600
400
200
0
Week
Month
1
3
Jan
5
7
Feb
9 11 13 15 17 19 21 23 25 27 29 31 33 35 37 39 41 43 45 47 49 51
Mar
Apr
May
Jun
Jul
Food-Borne Diseases .................................................... 3 - 30
Aug
Sep
Oct
Nov
Dec