PUBLIC HEALTH

Public health involves a kaleidoscope of issues and

comes under the purview of several government

agencies working in concert with each other. Among

these, the National Environment Agency (NEA) is the

government agency responsible for vector control

and food hygiene.

chapter4: p45

04chapter

TOWARDS ENVIRONMENTAL SUSTAINABILITYState of the Environment 2005 Report

Highly urbanised and a food

paradise, Singapore is vigilant

against vector-borne

and food-borne diseases.

Public Health

VECTOR CONTROL

Vectors are animals that carry disease that can infect humans.

Examples of vector-borne diseases are dengue fever, malaria,

typhus and bubonic plague. Their very names strike fear in

people’s hearts because they can cause immense suffering

and loss of life.

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

disease in Singapore, it is transmitted by Aedes mosquitoes

which breed in clean, stagnant water commonly found

in man-made containers in urban environments such as

flower pots. The presence of these conducive breeding

grounds and increased urbanisation contribute to an

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 DEN-

4), 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.

Mosquito-borne diseases

Despite Singapore’s location in the malaria-endemic tropics,

we are malaria-free. The majority of malaria cases (98.7%)

reported here are imported, i.e. contracted overseas.

One problem that we have, however, is dengue fever/dengue haemorrhagic fever. The main vector-borne

Photo by courtesy of Northwest Community Development Council

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.

chapter4: p47

No. of Cases2003 2004

Dengue Fever/Dengue Haemorrhagic Fever 4,788 9,459

Malaria 118 152

Local 5 2

Imported 113 150

Japanese Encephalitis 0 0

A pest control operator spraying rat poison into a rat burrow

Dengue fever is transmitted by the Aedes mosquito

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.

A PROACTIVE APPROACH

While the ability to react quickly to outbreaks is vital, NEA

takes a proactive approach that goes well beyond this.

It has a far-reaching programme to:

reduce vectors such as mosquitoes and rodents;

detect existing and emerging diseases carried by

vectors;

prevent vector breeding.

Meticulously monitoring the ground situation, conducting

wide-ranging research, enlisting the help of the

community, and engaging professional bodies to design

and build mosquito-proof or maintenance-free structures

to prevent mosquito breeding – these are all part and

parcel of NEA’s efforts.

Ground control

NEA’s vector control operations teams operate from its

five Environmental Regional Offices to conduct routine

inspections, preventive surveillance and education in

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

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.

chapter4: p49

Field officer enters survey data into PDA

Vector breeding details plotted in GIS

Spatial-temporal analysis by Situation Room

Early warning of hotspots.Deployment of operational staff to hotspots

Use of GIS in vector control operations

Laboratory officers identify& enter vector species Data in server

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 otherinstitutions, the EHI aims to develop disease preventionand control measures that are cost-effective.

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

dengue. This involves assessing patterns of disease with

respect to environmental factors. Surveillance and research

of diseases that threaten Singapore also prepares us to

detect emerging diseases.

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.

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

monitoring

Investigation of vector genetics, behaviour and

distribution

Study of mosquito-virus interactions

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

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.

1For more on ‘Mozzie Attack’, see Chapter 5.

2For more on ‘Rat Attack’, see Chapter 5.

chapter4: p51

The ‘Gravitrap’

The Gravitrap is one of several patents the EHI has filed since

its inception.

It is so called because it traps female mosquitoes that are

gravid, i.e. ready to lay eggs. This is an improved version of the

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

In order for the Gravitrap to help reduce mosquito populations,

thus contributing to reduced dengue transmission, it needs to

be deployed in large numbers over vast areas to compete

with other breeding sites. An initial field trial is planned with

10,000 pieces of the Gravitrap.

A volunteer checking for mosquito breeding

‘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.

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, Singaporegenerally has a low incidence of food-borne diseases.

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.

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.

chapter4: p53

Grade 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%

Foodshops %

Foodstalls in privateeating establishments %

Foodstalls in governmenthawker centres %

Upgrades available

Hawker centres3 are bastions of good local food, immensely

popular with Singaporeans from all walks of life. The HawkerCentres 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.

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

patrons have reacted with enthusiasm.

3For an explanation of hawker centres, see page 6.

The Hawker Centres Upgrading Programme is anambitious 10-year scheme to give major faceliftsto 110 of these hawker centres.

Adam Road hawker centre after upgrading

Adam Road hawker centre before upgrading

Upgraded toilet at Dunman food centre

CHALLENGES

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.

chapter4: p55

Singapore has been able to maintain a low or zeroincidence of most food-borne and vector-borne diseases.