Fewer dengue cases, but number may rise

THE number of dengue cases so far this year has nearly halved compared with the same period last year.

THE number of dengue cases so far this year has nearly halved compared with the same period last year, but the National Environment Agency (NEA) has urged Singaporeans to stay vigilant.

The NEA said there were 3,309 dengue cases from January to May, 45 per cent lower than the 6,015 for the same period last year.

The agency has warned, however, that dengue cases may rise in the coming months due to warmer weather and a rise in the transmission of the DENV-2 dengue virus strain.

There are four dengue strains, with DENV-2 and DENV-1 the most common in Singapore.

The warmer months of June to October could mean faster breeding and maturation cycles for Aedes mosquitoes, which carry the virus, and faster multiplication of the dengue virus in the mosquitoes, the NEA said yesterday.

The increasing proportion of DENV-2 cases may also lead to a spike in dengue cases.

"Historically, a change in the predominant dengue serotype has been followed by a spike in dengue cases," said the NEA spokesman, adding that the last switch, from DENV-2 to DENV-1, in March 2013 saw a sharp dengue outbreak that year.

The proportion of serotype 2 cases rose from 18.3 per cent last year to around 44 per cent as of mid-May this year.

Professor Tikki Pang, a visiting professor at the Lee Kuan Yew School of Public Policy, said people are more vulnerable in the face of a new dengue virus strain.

"Let us say that DENV-1 was the predominant serotype for many years or even months, this will mean that most people will have good immunity to DENV-1.

"But if the serotype then changes to DENV-2, for example, fewer people will have immunity to this serotype... so their immunity to DENV-2 would be lower and you end up with more cases."

Meanwhile, the NEA said that as of yesterday, a total of 22 mosquito breeding habitats were found and destroyed in the dengue cluster at Flora Drive and Flora Road in Loyang.

The high-risk area has had 65 cases this year, the most so far compared with other areas with active dengue transmission.

A Stop Work Order issued to the contractor of Inflora condominium at Flora Drive on April 30 has since been lifted, said the NEA.

"They were required to step up their housekeeping and mosquito control measures, as well as enhance the protection of their workers through the issuing of repellents and daily temperature screening," it said.

As of mid-May this year, the NEA has conducted more than 560,000 inspections and destroyed more than 6,000 mosquito breeding habitats, mostly in homes.

Nee Soon GRC MP Lee Bee Wah said MPs have also been going around to remind people to stay alert. "We need a combined effort to remind people to keep up with anti-mosquito drives and not relax."


This article was first published on June 16, 2015.
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