SINGAPORE - The dengue situation in Singapore seems to have eased this year compared with the record spate of cases early last year, but the authorities are urging people to keep their guard up to stamp out mosquito breeding grounds at home to avoid a spike in cases.

More than 2,000 dengue cases have been reported in Singapore so far this year, NEA said on Thursday (April 29) in a statement on the launch of the national dengue prevention campaign. In the first six months of last year, 10,000 dengue infections were reported.

NEA said it expects cases to increase towards the middle of the year, with the weather getting warmer. The warmer months of June to October accelerate the development of the Aedes mosquito, and also cause the virus to replicate faster in the insects. A higher transmission of dengue is usually observed during these months.

Two other factors could contribute to a worsening situation, NEA said.

The first is the high populations of the adult Aedes aegypti mosquito - the vector which spreads the dengue virus - in some areas. Another is the spread of dengue virus serotypes that were previously uncommon in the Republic. This means people would not have immunity against infection from these serotypes.

Getting infected with any of the four dengue serotypes induces immunity to that particular one, but does not confer long-term protection against the other serotypes.

Since 2016, the predominant dengue virus serotype in Singapore was serotype 2 (DenV-2), NEA said.

But, over the past two months, there has been an increase in the proportion of dengue cases and clusters for serotypes 3 and 4 (DenV-3 and DenV-4), which now make up more than 60 per cent of cases sampled.

No DenV-1 cases have been reported in Singapore between January and March this year.

"As DenV-3 has not been dominant since about three decades ago, and the incidence of DenV-4 has consistently been low, more people are susceptible to these two serotypes currently in circulation," NEA said.

The launch of the annual dengue prevention campaign ahead of the traditional mid-year peak dengue season aims to rally the community to deal with the dengue threat seriously, NEA said.

The islandwide campaign will be jointly led by local grassroots advisers and leaders, with support from NEA's dengue prevention volunteers, who will conduct house visits in dengue clusters and areas with high Aedes aegypti mosquito populations.

During these visits, they will advise residents on common mosquito breeding habitats, and share dengue prevention tips.

Mr Desmond Tan, Minister of State for Sustainability and the Environment, on Thursday marked the launch of the campaign by visiting several homes in Zhenghua division in Holland-Bukit Timah GRC to remind residents about "mozzie wipeout" to get rid of mosquito breeding areas.

He said that while the situation this year has eased compared with last year, the number of cases in recent weeks has started to climb. For instance, 131 cases were reported between April 18 and 24, up from the 112 cases between April 11 and 17, and 102 cases the week before.

The circuit breaker likely caused a spike in cases last year, he said, because there were greater chances of mosquitos biting people when they were always at home.

"With people going back (to work), we definitely hope that the number of incidents will go down," said Mr Tan. "But we have to prevent mosquito breeding in the first place. When a mosquito breeds, that poses a risk to the community - whether they are at home or walking around."