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After 9-week rise and 4,100 cases, dengue epidemic seems inevitable this year

Salma Khalik on 29 May 2019

The Straits Times


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SINGAPORE - The country is headed for a dengue epidemic this year, in spite of heightened efforts by the National Environment Agency to curb the spread of the Aedes mosquito.


There have been nine consecutive weeks of rising infections with almost 80 active clusters now - or more than double the number at the start of the month.


About 4,100 people have become sick with the mosquito-borne infection so far this year - more than for the whole of last year.


And the 379 people diagnosed last week is the highest weekly number in more than three years.


Another worrying trend is the high number of people who have the more serious dengue haemorrhagic fever - 31 cases so far this year, more than the whole-year numbers seen in each of the past five years.


An upswing can be caused by a change in the dominant dengue serotype, of which there are four. Although they all cause the same disease, being infected by one serotype confers immunity only against that, and not against the other three. So when the dominant virus changes, most of the people infected in previous years would not have immunity against the new serotype.


However, the Ministry of Health (MOH) said the dominant strain today, Den-2, has been dominant since 2016. The World Health Organisation says Den-2 is "frequently associated with severe disease accompanying secondary dengue infections".


The disease has already resulted in three deaths this year, all older people in their 70s.


The two biggest clusters today are both around Woodlands Avenue 6.


In one, 143 people have been infected, with 31 falling ill in the past fortnight. In the other, 119 people have been infected, of whom 32 were diagnosed in the past two weeks. The large numbers infected in the past fortnight indicates that the virus is still actively spreading.


The NEA has been intensifying its efforts to eradicate the Aedes aegypti mosquito and possible breeding areas, but warns that the number of infections is likely to rise as the warmer months approach.


In the first three months, its officers detected 3,100 breeding sites, or 39 per cent fewer than in the previous quarter, but this did not signal a fall in infections. On its website, NEA says: "The number of weekly reported dengue cases have been on an upward trend, and have more than tripled in the past nine weeks."


The number of mosquitoes, and hence infections, can be expected to increase with the advent of warmer months as warm weather accelerates the breeding and maturation cycles of the mosquitoes.


Symptoms of dengue include a sudden onset of fever that lasts two to seven days, severe headache with pain behind the eyes, joint and muscle pain, skin rash, nausea and vomiting.


About one in five people diagnosed usually ends up in hospital. There is no specific treatment for dengue. Those who get the more dangerous dengue haemorrhagic fever or dengue shock syndrome might require blood transfusions and electrolyte replacements.


The biggest dengue epidemic Singapore has ever faced was in 2013, when more than 22,000 people fell ill with the mosquito-borne disease.


The most deaths was in 2005, when 25 people died because of a mosquito bite.


Source: The Straits Times © Singapore Press Holdings Limited. Reproduced with permission.



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