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chapter
TOWARDS ENVIRONMENTAL SUSTAINABILITY
State of the Environment 2005 Report
04
Public Health
Highly urbanised and a food
paradise, Singapore is vigilant
against vector-borne
and food-borne diseases.
PUBLIC HEALTH
VECTOR CONTROL
Public health involves a kaleidoscope of issues and
Vectors are animals that carry disease that can infect humans.
comes under the purview of several government
Examples of vector-borne diseases are dengue fever, malaria,
agencies working in concert with each other. Among
typhus and bubonic plague. Their very names strike fear in
these, the National Environment Agency (NEA) is the
people’s hearts because they can cause immense suffering
government agency responsible for vector control
and loss of life.
and food hygiene.
Thanks to Singapore’s clean environment, many vector-borne
diseases commonly found in tropical countries are rare here.
However, we must continue to keep a constant guard against
vectors for two major reasons:
Given the right conditions, some vectors (for instance
Aedes mosquitoes and rats) thrive in an urban environment;
Singapore has one of the world’s highest population
densities; any outbreak of vector-borne disease has the
potential to spread very rapidly.
Country
Population/sq km
Macau
24,111
Hong Kong
6,366
Singapore
6,300
India
300
United Kingdom
242
Source: 2001 UK Census on Population Densities
Photo by courtesy of Northwest Community Development Council
Mosquito-borne diseases
Despite Singapore’s location in the malaria-endemic tropics,
disease in Singapore, it is transmitted by Aedes mosquitoes
we are malaria-free. The majority of malaria cases (98.7%)
which breed in clean, stagnant water commonly found
reported here are imported, i.e. contracted overseas.
in man-made containers in urban environments such as
flower pots. The presence of these conducive breeding
One problem that we have, however, is dengue fever/
grounds and increased urbanisation contribute to an
dengue haemorrhagic fever. The main vector-borne
increase in this disease.
The low-down on dengue
Dengue fever and dengue haemorrhagic fever are caused by one of four virus serotypes (DEN-1, DEN-2, DEN-3, and DEN4), of the genus Flavivirus. Infection with one serotype does not make a person immune to infection from the other serotypes.
Primarily a tropical disease, dengue is spread mainly by Aedes aegypti, a day-biting mosquito that prefers to feed on
human blood.
chapter4: p47
This year, several countries have reported an increase in
dengue cases from the previous year. Singapore too, saw
a doubling in the number of cases compared to 2003.
No. of Cases
2003
2004
Dengue Fever/Dengue Haemorrhagic Fever
Malaria
Local
Imported
Japanese Encephalitis
4,788
9,459
118
152
5
2
113
150
0
0
Dengue fever is transmitted by the Aedes mosquito
Rodent-borne diseases
Rats are another vector that thrives in an urban
environment. This is because humans often create
favourable conditions for them, for example by
indiscriminately littering food wastes.
Local rodent species in Singapore are the Norway rat
(Rattus norvegicus) and roof rat (Rattus rattus diardii). Rats
have the potential to spread several diseases, including
rat bite fever, salmonellosis and leptospirosis. They can also
host rat fleas that transmit plague.
In the interest of public health, rodent population has to be
kept low through effective rodent control by denying them
food and nesting places. Therefore, great emphasis is placed
on environmental sanitation and hygiene in Singapore.
A pest control operator spraying rat poison into a rat burrow
A PROACTIVE APPROACH
wide-ranging research, enlisting the help of the
community, and engaging professional bodies to design
While the ability to react quickly to outbreaks is vital, NEA
and build mosquito-proof or maintenance-free structures
takes a proactive approach that goes well beyond this.
to prevent mosquito breeding – these are all part and
It has a far-reaching programme to:
parcel of NEA’s efforts.
reduce vectors such as mosquitoes and rodents;
Ground control
detect existing and emerging diseases carried by
vectors;
NEA’s vector control operations teams operate from its
prevent vector breeding.
five Environmental Regional Offices to conduct routine
inspections, preventive surveillance and education in
Meticulously monitoring the ground situation, conducting
dengue-sensitive neighbourhoods. Wherever outbreaks
occur, additional teams are deployed to contain the
outbreak quickly.
5 Regional Office Locations
North West Regional Office
North East Regional Office
South East Regional Office
Central Regional Office
South West Regional Office
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Command and conquer
While our field officers are familiar with the ground
situation, certain trends and irregularities can be identified
only after surveillance data are analysed. This important
function is fulfilled by a command centre. There, using
the Geographical Information System, our vector control
specialists process information on the locations of vector
populations and the incidences of vector-borne diseases.
Using a graphical inter face, they monitor the
development and movement of hotspots with high
mosquito breeding or dengue fever cases. Such
information is then communicated to the ground
operations teams so that they can zoom in quickly to
tackle the problem before it grows out of control.
Use of GIS in vector control operations
Field officer enters survey data into PDA
Laboratory officers identify
& enter vector species
Data in server
Vector breeding details plotted in GIS
Spatial-temporal analysis by Situation Room
Early warning of hotspots.
Deployment of operational staff to hotspots
Know the enemy
Important as work on the ground is, it needs to be
supported by upstream research. To this end, the
Environmental Health Institute (EHI) was formed in 2002.
Through its own research and partnering with other
institutions, the EHI aims to develop disease prevention
and control measures that are cost-effective.
Through its own research and partnering with other
institutions, the EHI aims to develop disease prevention
and control measures that are cost-effective.
EHI research areas
Vector Support and Research
Assessment of vector control tools, including pesticides
Reference Laboratory for Vectors of Singapore
Development of new tools for vector control and
The role of the EHI is to investigate and research infectious
diseases whose transmission is governed mainly by
environmental factors. Besides developing tools for vector
control and diagnostics, the EHI seeks to understand the
epidemiology of endemic vector-borne diseases such as
monitoring
dengue. This involves assessing patterns of disease with
Investigation of vector genetics, behaviour and
respect to environmental factors. Surveillance and research
distribution
of diseases that threaten Singapore also prepares us to
Study of mosquito-virus interactions
detect emerging diseases.
Surveillance of vectors for other diseases like West
Nile and Hanta Viruses.
Molecular Microbiology
Development of tools for rapid and early diagnostics
and epidemiology of Singapore
Monitoring of dengue virus dynamics
Development of Dengue Reference Collection in
Singapore
Indoor Air Quality and Legionella
Study on Legionella virulence
Risk assessment of indoor air quality
Investigation of new parameters for indoor air quality
In the event of an actual outbreak, the EHI would provide
information on the vectors involved, as well as identify and
screen vector and virus samples.
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The ‘Gravitrap’
The Gravitrap is one of several patents the EHI has filed since
In order for the Gravitrap to help reduce mosquito populations,
its inception.
thus contributing to reduced dengue transmission, it needs to
be deployed in large numbers over vast areas to compete
It is so called because it traps female mosquitoes that are
with other breeding sites. An initial field trial is planned with
gravid, i.e. ready to lay eggs. This is an improved version of the
10,000 pieces of the Gravitrap.
ovitrap which kills only the offspring but does not capture the
gravid female mosquitoes.
Advantages of the Gravitrap are that it:
Captures the egg-laying females as well as their offspring
Requires minimal maintenance (non-reliant on moving
structural parts)
Will not turn into a breeding source with neglect (foolproof)
Is user-friendly
Can be mass-produced
Is relatively cheap
Is disposable
Community warriors
Over the years, NEA has embarked on a series of
programmes to raise public awareness and mobilise our
community to help reduce the vector population. As part
of this relentless effort, two pilot programmes were launched
in 2004.
‘Mozzie Attack’ aims to rally the public to eliminate
stagnant water and household objects that hold
stagnant water, as these are good breeding habitats
for Aedes mosquitoes. Volunteers organised exhibitions,
door-to-door visits and talks to get the message across
to residents1.
‘Rat Attack’ declared war on rats. It demonstrates
effective ways to reduce rodent infestation in residential
neighbourhoods, and emphasises the need for total
community involvement to sustain rodent control2.
NEA intends to roll out these programmes to all
neighbourhoods in Singapore eventually.
1
For more on ‘Mozzie Attack’, see Chapter 5.
2
A volunteer checking for mosquito breeding
For more on ‘Rat Attack’, see Chapter 5.
FOOD HYGIENE
Besides her reputation for cleanliness, Singapore is also
renowned as a food paradise. Dishing up a spectacular
variety of cuisines are a staggering 16,000 dining
establishments, ranging from fine restaurants to humble
hawker stalls. Every one of these dining establishments is
closely monitored for hygiene by NEA.
Because of this high standard of food hygiene, Singapore
generally has a low incidence of food-borne diseases.
‘Germ warfare’
Because of this high standard of food hygiene, Singapore
generally has a low incidence of food-borne diseases.
This is particularly reassuring in a country where eating
out is an intrinsic part of the local lifestyle and tourist
experience alike.
Besides stringent licensing, inspection and enforcement,
NEA employs several other measures to encourage good
food hygiene practices at food outlets.
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Grade expectations
All eating establishments and foodstalls are graded on
their housekeeping, cleanliness, pest infestation, food
hygiene and personal hygiene of its food handlers. (The
grade has no bearing on the taste of the food). Displaying
the grade for each food outlet lets customers make
informed choices.
Grade
Foodshops %
Foodstalls in private
eating establishments %
Foodstalls in government
hawker centres %
Year
A (Excellent)
B (Good)
C (Average)
D (Poor)
1999
29.67%
49.39%
20.63%
0.31%
2004
42.49%
47.48%
9.95%
0.08%
1999
2.51%
33.37%
64.01%
0.11%
2004
15.40%
42.91%
41.68%
0.01%
1999
1.14%
38.61%
59.52%
0.73%
2004
10.15%
45.70%
43.70%
0.45%
In addition, a Straight A’s Programme has been
implemented to enhance food hygiene standards at
school cafeterias and air-conditioned foodcourts. A major
component in this programme is a self-check system for
stall operators to track their own performance. With inputs
from NEA, foodcourt managers also carry out regular audits
and reviews.
Adam Road hawker centre after upgrading
Upgrades available
Hawker centres3 are bastions of good local food, immensely
popular with Singaporeans from all walks of life. The Hawker
Centres Upgrading Programme is an ambitious 10-year
scheme to give major facelifts to 110 of these hawker
centres, while retaining their unique charm and
Singaporean identity.
Adam Road hawker centre before upgrading
The Hawker Centres Upgrading Programme is an
ambitious 10-year scheme to give major facelifts
to 110 of these hawker centres.
The upgrading works are not merely cosmetic. They include
re-tiling, enlarging the stalls, improving the toilets and refuse
bin centres, as well as overhauling the ventilation, electrical,
exhaust and plumbing systems. The result: premises that
are cleaner, brighter, airier and more easily maintained.
Patrons can thus look forward to tucking in amid more
pleasant surroundings and higher standards of hygiene.
The total cost of the programme is expected to be S$420
million. To date, 34 centres have been upgraded, and
Upgraded toilet at Dunman food centre
3
For an explanation of hawker centres, see page 6.
patrons have reacted with enthusiasm.
chapter4: p55
CHALLENGES
Singapore has been able to maintain a low or zero
incidence of most food-borne and vector-borne diseases.
Singapore has been able to maintain a low or zero
incidence of most food-borne and vector-borne diseases.
It is an extremely safe place for residents, tourists and
business investors.
But such diseases are opportunistic and our community
cannot afford to let up on efforts to prevent them. The flow
of different dengue virus strains among countries in endemic
zones will continue to be a challenge to Singapore, which
is situated in the midst of an endemic region.
We also need to be vigilant against emerging diseases.
These could include West Nile Virus, Nipah virus, Yellow
Fever and Japanese Encephalitis. NEA will continue its
surveillance and research programmes in these areas.
We have laid a foundation in prevention measures, early warning systems and research. But the challenges ahead underscore the
need for us to improve further in these areas, so that we always remain one step ahead of diseases.