THERE has been a sudden surge of dengue fever this year, with more than 200 cases diagnosed last week - the highest weekly number in more than a year and sparking a possible epidemic.
The epidemic threshold is 165 cases a week, so this sudden jump from 134 cases in the first week of the year is alarming, especially since this is not the typical dengue season. The increase has continued into this week with 135 cases as of 3pm yesterday.
The Ministry of Health said 82 patients have been hospitalised for dengue this year.
A spokesman for the National Environment Agency (NEA) said the spike is "unusual". Dengue cases are usually high during the hot months from April to October, when the female Aedes mosquito reproduces faster.
She added that the 342 cases so far this month is 2.5 times the number compared to the same period last year.
The spike in cases could signal a possible change in the predominant virus.
There are four dengue viruses. In Singapore, Den-2 has been dominant for the past five years, causing 75 per cent of infections.
Den-1 typically accounts for less than 25 per cent of infections, but now accounts for 30 per cent, the spokesman said. Because Den-1 has not been active lately, she said it is a strain "the community has lower immunity against".
This was the dominant strain responsible for the most recent dengue epidemic of 2005, in which more than 14,000 people were infected and 27 died.
This Den-1 virus is most active in four areas: Telok Kurau, Hougang Avenue 1, Kaki Bukit and Geylang Lorong 11.
At Telok Kurau, which is the biggest cluster today with 50 infections, NEA officials found 40 breeding spots in 33 homes. The majority were found in ornamental and domestic containers.
The spokesman said the NEA will send out more people to areas where Den-1 is active, and set traps to catch adult mosquitoes.
Meanwhile, the NEA has alerted the Inter-Agency Dengue Task Force, which includes the Land Transport Authority, the HDB, the National Parks Board and town councils, to step up checks.
While dengue is endemic in Singapore, it tends to peak every six to seven years. Symptoms include sudden fever, aching joints, headaches, rash and nausea.
Those who have had dengue before and are infected by a different strain tend to be more sick.
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