Weekly dengue cases drop to year low, after historically severe outbreak

File photo of the Aedes aegypti, the main mosquito species that transmits dengue in Singapore.
File photo of the Aedes aegypti, the main mosquito species that transmits dengue in Singapore. (FILE PHOTO: Getty Images)

SINGAPORE — The number of weekly reported dengue cases dropped to 228 last week, the lowest weekly case number in 2020, as the severity of the outbreak continues to abate after a historic high.

The National Environment Agency (NEA) said a media release on Friday (18 December) that, as of Thursday, there have been 34,844 reported dengue cases this year, far surpassing the previous high of 22,170 reported for the whole of 2013.

However, the latest weekly dengue case number is about seven times lower than the peak of 1,792 seen in July. Last week’s figure is also the fourth successive week where case numbers have gone below 300.

“NEA would like to thank all our community stakeholders who have played a key role in leading dengue prevention efforts during this historic dengue outbreak year, in spite of the exceptional challenges posed by COVID-19,” said Chew Ming Fai, NEA’s deputy chief executive officer and director-general of public health.

“The steady decline in weekly dengue case numbers since August shows how far we have come together in fighting dengue. Community support will always be an important part of our fight against dengue, and we must continue to keep up our efforts to eliminate mosquito breeding habitats and take steps to protect ourselves from dengue.”

Efforts to bring case numbers down from peak in July.

The year 2020 started with high weekly dengue cases of between 300 and 400, and the relative dominance of the more unusual dengue virus serotype (DENV-3) in the first four months of the year. Weekly cases rose sharply in May, shortly after the start of the COVID-19 circuit breaker, and peaked at 1,792 cases in July.

Community stakeholders began to mobilise efforts to check households for potential mosquito breeding habitats, and encourage residents to use insect repellent and insecticides. Town councils were also mobilised to step up inspections and vector control operations in the common areas of estates.

Overall, NEA has closed about 98 per cent, or 3,003 of 3,060, of the dengue clusters notified since the beginning of this year. However, large dengue clusters remain at Tampines Street 11, Geylang Road, Bukit Batok Street 21 and Admiralty Drive, where intensive vector control operations are ongoing.

NEA added that the present weekly case number of between 200 and 300 is still relatively high for this time of the year. While the figure is below the weekly case number in 2019, it is still about three times the average number of cases reported in the preceding three years (2016 to 2018), which saw fairly low dengue case numbers.

“Two other indicators that bear watching are the 20 per cent increase in adult Aedes aegypti mosquito population in November – there are currently over 230 residential areas with high Aedes aegypti mosquito population, and the relatively higher proportion of DENV-3 and DENV-4 serotype cases which are less common in Singapore,” it said in the media release.

“We therefore urge everyone to stay vigilant against the dengue threat, and to sustain the good efforts and efforts so far in stemming dengue transmission.”

Extra steps to prevent mosquito breeding during staycation

As there is a higher tendency for water to remain stagnant in unused premises, those households planning to go on staycation during the December holidays should take the following extra steps to prevent mosquito breeding:

  • Cover all toilet bowls at home, and seal off overflow pipes of the flushing cisterns;

  • Cover all floor traps;

  • Add Bti insecticide to places where mosquitoes could potentially breed, and places where stagnant water cannot be removed;

  • Clear debris and blockages, and place Bti insecticide in roof gutters and drains within compounds;

  • Turn over all water storage containers and wipe the rims dry;

  • Ensure that flower pots, plates and trays do not collect water, after watering the plants;

  • Ask a relative or close friend to check the home regularly for stagnant water, if you will not be around for a long period of time;

  • Leave contact details with neighbours or the neighbourhood police post/centre, so that you can be easily reached if needed.

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