SINGAPORE - Dengue cases have fallen to their lowest level this year following the largest outbreak in Singapore's history.

There were 228 reported last week, about seven times lower than the peak of 1,792 cases in July.

Last week's figure, released on Friday (Dec 18) by the National Environment Agency (NEA), also marks the fourth successive week where cases have dipped below 300.

The death toll from dengue hit a record high of 29 this year, with possible causes of the historic outbreak including the dominance of an unusual strain and more people being bitten by mosquitoes while staying at home during the Covid-19 circuit breaker.

The cumulative number of dengue cases this year - as of Thursday - stands at 34,844, surpassing the high of 22,170 cases in 2013.

But cases have declined steadily from August due to efforts by the community to bring infections under control, said Mr Chew Ming Fai, deputy chief executive officer and director-general of public health at the NEA.

These included frequent checks by residents for potential mosquito breeding habitats and inspections by town councils.

Historic year of dengue cases

This year's historic dengue outbreak was due to various factors, some Covid-19 related, added the agency. It started with high weekly infections of between 300 and 400 as well as the dominance of the serotype DENV-3, an unusual strain of the virus, in the first four months of this year. There are four dengue serotypes, with the outbreaks here typically caused by DENV-1 and DENV-2.

Cases spiked in May, shortly after the start of the circuit breaker, and peaked in July before declining steadily.

As of Thursday, there were 57 dengue clusters reported, seven fewer than in the previous week. Since the beginning of the year, the agency has closed about 98 per cent of the dengue clusters.

However, the NEA cautioned against complacency as the weekly case number remains relatively high for this time of the year. Although below last year's figure, it is three times the average number of cases reported from 2016 to 2018.

The agency attributed this to the 20 per cent increase in the adult Aedes aegypti mosquito population in November as well as the relatively higher proportion of DENV-3 and DENV-4 serotype cases, which are less common in Singapore.

As at Thursday, more than 230 residential areas have high Aedes aegypti populations with large dengue clusters in Tampines Street 11, Geylang Road, Bukit Batok Street 21 and Admiralty Drive.

The NEA said it will continue to conduct preventive inspections with its partners to remove mosquito breeding habitats.

It will also focus on areas with high Aedes aegypti populations as well as construction sites and industrial premises that are close to residential areas.

Between January and last month , the NEA conducted around 954,000 inspections for mosquito breeding around the island.

These uncovered about 21,500 mosquito breeding habitats and led to 7,060 enforcement actions taken against owners of the premises.

Repeat offenders

Heavier penalties for households which commit repeated mosquito breeding offences were introduced from July 15. Since then, around 260 of the NEA's inspections were of residential premises.

There were also 18 contractors charged in court with repeat offences.

Mosquito-proof your home before staycations

Due to the higher chance of stagnant water pooling in unused premises, the agency added that members of the public should take precautions to prevent mosquito breeding before going on staycations.

These include ensuring that flower pots, plates and trays do not collect water, as well as covering toilet bowls and floor traps.

More information can be found on the NEA website. "The risk of dengue is real given that the virus is endemic in Singapore, the historic dengue outbreak seen this year, and with a sizeable proportion of residents still working from home," said the agency.

"Residents, especially those residing in dengue cluster areas, should do their part and carry out the three protective actions against dengue - spray insecticide in dark corners around the house, apply insect repellent regularly, and wear long-sleeve tops and long pants."