New purple banner to signal areas with high Aedes population

With dengue cases rising faster than they did last year, people living in areas with a persistently high Aedes aegypti mosquito population are reminded to remain vigilant, with the help of a new purple banner.

Colour-coded banners - purple, yellow, red and green - are being used by the National Environment Agency (NEA) as part of its Dengue Community Alert System.

The red, yellow and green banners communicate to the public the presence of dengue in the neighbourhood.

Red banners are put up in high-risk areas where there are more than 10 cases of dengue.

Yellow banners are for areas where there are fewer than 10 cases of dengue, and green banners are put up where there are no new cases.

The new purple banner is put up in places with persistently high populations of Aedes mosquitoes and with a greater risk of a cluster forming.

The banners complement existing vector control operations and community outreach efforts.

Close to 3,000 dengue cases have been reported since the start of this year, NEA said yesterday.

This increase is faster than the rise in cases last year. More than 2,000 dengue cases were reported only at the end of April last year.

Weekly reported dengue cases have also been rising sharply, with 444 cases recorded for the week ending March 26 - 20 cases more than in the previous week.

There are also currently 112 active dengue clusters.

About 101,000 inspections for mosquito breeding were carried out islandwide between January and February, with NEA uncovering about 2,600 mosquito breeding habitats.

NEA said there are three main reasons contributing to the surge.

First, there is a high Aedes aegypti mosquito population detected in the community, with the population of mosquitoes last month standing at 17 per cent higher, compared with February last year.

Second, the mosquitoes appear to be carrying the more uncommon DenV-3 serotype of dengue. The DenV-3 serotype has been detected in large dengue clusters across the island.

Most recovered dengue patients in Singapore would have immunity against the DenV-1 and DenV-2 serotypes, which are two of the four distinct dengue virus variations, and the variations most commonly seen here.

Less common strains, like DenV-3 , would increase the risk of an outbreak.

Finally, NEA said more people are staying at home, which gives the day-biting mosquito more time to prey on them.

It also warned that the warmer months from June to October will compound this surge.

Warmer temperatures accelerate the development of the Aedes mosquito, and also cause the virus to replicate faster in the insects.

With this surge in dengue cases, NEA yesterday launched the annual dengue prevention campaign early - ahead of the traditional mid-year peak dengue season.

As part of the launch, Minister of State for Sustainability and the Environment Desmond Tan visited several blocks in Pasir Ris Drive 6 - an area detected to have a persistently high population of Aedes mosquitoes - to unveil the purple banner.

Mr Tan said: "Even if we are in the midst of a Covid-19 pandemic, dengue remains a clear and serious public health threat."

The aim of the banner is to rally the community to take positive actions to prevent the breeding of mosquitoes, Mr Tan added.

Among other steps, residents can prevent the breeding of mosquitoes by lifting and emptying flower pot plates, and keeping roof gutters clear of leaves.

The annual dengue prevention campaign will also see local grassroots advisers and leaders, with support from NEA's dengue prevention volunteers, conducting house visits in dengue clusters and areas with high Aedes aegypti mosquito populations.

They will be disseminating information on mosquito breeding and distributing repellent during the house visits.