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Dengue cases hit 4,000, double from same period last year

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Number is double from same period last year; factors include rise of less common dengue virus serotype and warmer temperatures

More than 4,000 people in Singapore have been infected with dengue fever this year - double the number of cases reported for the same period last year.

The surge in cases, ahead of the traditional peak dengue season between June and October, has been fuelled by several factors - the rise of a less common dengue virus serotype, as well as warmer temperatures and more rain that caused the population of the Aedes aegypti mosquito to multiply.

"Entering the warmer months, there could be more instances of transmission," said Environment and Water Resources Minister Masagos Zulkifli at the launch of the National Dengue Prevention Campaign yesterday.

The National Environment Agency's (NEA) annual campaign typically begins next month or in May but started earlier this year in view of the grimmer dengue outlook. The island has seen 300 to 400 new cases a week since the start of the year.

There are now about 100 active dengue clusters islandwide, including 28 "red" clusters that have at least 10 cases. Parts of Jurong West and Ang Mo Kio Avenue 10 are in these high-risk areas.

Dengue fever is caused by four different virus serotypes or strains.

Outbreaks here tend to be caused by the DenV-1 serotype as well as DenV-2, the main dengue virus serotype. But DenV-3 infections have been rising in the past four months. Last month, they made up 48 per cent of cases, almost double the 26 per cent for DenV-2 cases.

Mr Masagos said since Singapore has not had a dengue outbreak driven by DenV-3 in almost three decades, the population's immunity to this serotype is lower.

It is "still too early" to tell if there has been a switch of predominant dengue virus type, and the NEA is monitoring the situation closely, he added.

"We have a less common dengue virus serotype emerging and lower immunity against it, and second, we have more Aedes mosquitoes carrying this virus.

"This has resulted in a higher number of dengue cases, which in turn increases the chances of dengue transmission. So that is the third reason for the surge in dengue cases we are seeing...

"If the three factors persist, this number could rise beyond the historical weekly peak of 891 cases recorded in July 2014, during the peak season."

Over the past three years, the detection rate of Aedes mosquito larval habitats in homes has gone up by 90 per cent, which Mr Masagos attributed to "better surveillance and analytics capabilities".

Everyone must continue to do their part to keep the community safe, Mr Masagos said.