Total count of dengue fever cases stand at 20,458 with many clusters found in the north and east of Singapore

Singapore currently sees a record of 20,458 dengue fever cases in 2020 and main clusters localised in the east and north. The week of 19 – 25 Jul 2020 also saw a sharp spike in cases as compared to the same week in the last four years. 

As of Tuesday (28 Jul) 3pm, the National Environment Agency (NEA) recorded 191 new cases. Its total year count stands at 20,458 for the first 30 e-weeks of 2020, more than the total count of 15,998 cases in 2019. 

NEA has identified more than 400 clusters, with hotspots centralised in the north and east. 

Technically, a dengue cluster indicates a locality with active transmission where intervention is targeted. It is formed when two or more cases have onset within 14 days and are located within 150m of each other (based on residential and workplace addresses). 

There are three levels of concentrations: red, yellow and green. 

Red indicates a high-risk area with 10 or more cases, while yellow is a high-risk area with less than 10 cases. 

Dengue fever clusters have been found in the north and east since 2015, says NEA

Some of the biggest hotspots this year have been centred around areas such as Aljunied, Geylang in the east and Woodlands Road in the north, the spokesperson for the NEA said. 

When asked for the reason, the representative said that the eastern part of Singapore is “highly populated and urbanised”, which is why dengue transmission is generally higher in the east.

“The primary vector of dengue, the Aedes aegypti mosquito, is very well-adapted to our urban environment, preferring to breed, mate and feed near human dwellings,” the spokesperson added. 

According to data collected by the agency, the pattern of greater dengue clusters in the east and north has been recorded since 2015.

It is found that top clusters each year since then have been in the east, in areas such as Tampines, Geylang and Bedok, and in the north, in neighbourhoods in Woodlands, Yishun and Sembawang.

On the other hand, certain parts of the west, such as Pioneer, have seen no clusters at all in 2020. Bukit Panjang is the exception with it being one of the biggest clusters. 

“Dengue hotspots are not confined to the east. Urbanised and high-density areas in the north and west have also seen mosquito breeding habitats and high numbers of dengue cases,” said the spokesperson. 

The last level – green – is clusters under surveillance. These are areas that have reported no new cases, and will be monitored for the next 21 days. 

Weekly number of cases from 14 Jun have been four-digits, while daily cases since 22 Jul have been three-digits. 

Each e-week from 14 Jun has recorded numbers over 1000, with the total count standing at 20,458 for the first 30 e-weeks, according to the Communicable Diseases Division of Ministry of Health

For the past four years for the e-week ending 25 Jul, cases have been relatively controlled – with the highest at 663 in 2019, and the lowest at 91 in 2015. 

In sharp contrast, this e-week in 2020 recorded a total of 1794 cases. 

Experts cite the factors that cause the high numbers in 2020

They say it is partly due to Covid-19-related factors and partly because of a new strain of dengue that many people are more vulnerable to. 

Associate Professor Lim Poh Lian, a senior consultant at the National Centre for Infectious Diseases (NCID), said that clusters are those areas of higher urban population density, since Aedes mosquitoes “thrive” in housing areas.

Dr Alex Cook, an associate professor at Saw Swee Hock School of Public Health in the National University of Singapore (NUS), elaborated that “urban settings could result in “warmer microclimates” because of dense building infrastructure.

“Mosquitoes develop faster in warmer temperatures, meaning the cycle from one generation of human infection to the next is shorter. The virus also replicates faster at higher temperatures during the extrinsic incubation period, with the same effect,” he said.

Some other causes include the presence of old buildings and a poor immunity to a dengue serotype or strain called DENV-3 that is newly being transmitted. 

Dr Borame Sue Lee Dickens, a senior research fellow at the NUS Saw Swee Hock School of Public Health, said that the design of older buildings in Singapore provides more opportunities for small pools of water to form.

“There are more crevices from building wear and tear, and now-defunct design features present similar opportunities for mosquito breeding such as the holes for bamboo poles (where people hang laundry outside windows of high-rise flats),” she said. 

Lifestyle habits that can prevent the spread of dengue fever

NEA advises the public to remove any stagnant water in their homes and immediate surroundings, such as corridors and gardens. This is to destroy any mosquito breeding habitats and break the cycle of dengue transmission. 

Residents living in dengue cluster areas are advised to spray insecticide in dark corners around the home, such as behind curtains and under beds, apply mosquito repellent regularly and wear long-sleeve tops and long pants, to protect themselves from mosquito bites.

As the Aedes mosquito’s life cycle can be as short as seven days, it is important to Do the Mozzie Wipeout at least once a week.

The NEA has enhanced penalties to curb this spread. These have been imposed on households, construction sites and Town Councils. 

Heavier penalties on offences committed by households include:

• Repeated mosquito breeding offences
• Multiple mosquito breeding habitats detected in a single inspection; and
• Mosquito breeding detected after having received a legal notice from NEA.

Should anyone notice these symptoms showing, it could be suggestive of dengue fever and they should seek medical attention immediately. 

The symptoms include: 

• Sudden onset of fever for two to seven days;
• Severe headache with retro-orbital (behind the eye) pain;
• Joint and muscle pain;
• Skin rashes;
• Nausea and vomiting;
• Bleeding from the nose or gums;
• Easy bruising of the skin

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