SINGAPORE — Weekly dengue cases in Singapore have fallen by about 70 per cent since a peak in May this year, but residents must still remain vigilant to prevent a second dengue surge, the National Environment Agency (NEA) said.

In a statement on Monday, it added that 95 per cent of the dengue clusters reported since the start of the year have been closed or no longer active.

There were 427 dengue cases reported last week, 46 fewer than the week before, NEA said. This is a further drop since the end of last month, when weekly cases dipped below 600.

As of last Friday, there were 142 dengue clusters reported, six clusters fewer than the 148 in the previous week.

In the last three weeks, clusters along Ghim Moh Road, Bedok Reservoir Road and Clement Road have been closed, NEA said.

"Overall, we have closed about 95 per cent, or 2,563 of 2,705, of the dengue clusters notified since the start of this year." 

However, it continues to observe clusters with a "relatively fast rate of transmission", including along Clementi West Street 2, Jurong East Street 21, Jurong West Avenue 5 and Rivervale Crescent in Sengkang.

As of last Friday, there have been more than 28,500 dengue cases reported here this year, the agency said.

Dengue cases started to rise in February, prompting NEA to bring forward its National Dengue Prevention Campaign.

This involved putting up new dengue alert banners and maintaining a "high tempo of preventive inspections to remove breeding habitats", it said.

The Inter-Agency Dengue Task Force carried out 200,000 inspections in the first half of the year, on top of the 409,000 carried out by NEA.

To complement the dengue control efforts, NEA also began releasing male Wolbachia-Aedes mosquitoes at eight more field sites since July.

UPDATE ON PROJECT WOLBACHIA

Baey Yam Keng, who spoke to reporters at a Wolbachia mosquito release session in MacPherson on Monday, urged the public "to keep on our toes to do our part" as many active dengue clusters still remained despite the drop in cases.

The Senior Parliamentary Secretary for Sustainability and the Environment helped to release the insects under the ongoing initiative by NEA and other stakeholders to introduce male mosquitoes infected with Wolbachia bacteria into specific sites in Singapore.

The male Wolbachia-Aedes mosquitoes, which do not bite, are released into neighbourhoods to breed with female Aedes mosquitoes in the areas. Eggs produced by that pairing do not hatch, thereby reducing the reproduction of Aedes mosquitoes.

In July, the Wolbachia project was expanded to eight new neighbourhoods, including Geylang. The new expansion added 1,400 Housing and Development Board (HDB) blocks to the project, covering about 31 per cent of all HDB blocks in Singapore, NEA added.

Mr Baey said that residents will notice an increase in mosquitoes in these areas but over time, they will get used to it.

When residents see their dengue cluster warning change from red to green, “they really see the results of all these mosquitoes, and the ground buy-in and support is slowly picked up (from there)", he added. The dengue cluster warning may be shown on banners put up in the areas, for instance, with red representing high-risk areas and green meaning that there are no new cases.

Mr Baey thanked grassroots advisers and leaders for helping to explain the project to residents so that more people may understand and support it.

As of now, NEA has said that there are no plans to expand the project further​​​​​​.

VIGILANCE 'CRITICAL'

Despite Singapore "moving beyond the traditional dengue peak season", NEA said that "continued vigilance remains critical as weekly dengue cases and the Aedes aegypti mosquito population... remain high".

Weekly dengue cases could continue to remain high beyond the peak dengue season from June to October, because "we still see dengue transmission in many areas across the island", the agency added.

These include large dengue clusters located along Boon Lay Avenue, Aroozoo Avenue near Kovan, Hougang Avenue 1, Jelapang Road in Bukit Panjang, Bishan Street 11 and Marine Crescent in East Coast.

It encouraged the public to do their part in reducing dengue by taking precautions against mosquito bites — such as by applying insect repellent regularly — and reducing places where the insects can breed, such as by keeping pails overturned and changing the water in vases.