Singapore

1,678 dengue cases last week; 370 active clusters mostly in the east

The dengue outbreak continues to surge, with 1,678 people diagnosed with the viral infection last week, a 16 per cent increase over the previous week's figure of 1,449.Such high infection numbers have not been seen here before.

A total of 17,249 people have been infected as of 3pm on Monday. This already exceeds the annual infection numbers for all previous years except for the epidemic of 2013-2014.

Experts warn that the number this year is likely to surpass even the 22,170 infections of 2013. At least 16 people have died from dengue this year.

There are more than 370 active clusters, mostly in the east, with 133 considered high risk, while 17 have more than 100 people infected.

Professor Duane Gubler, a dengue expert at the Duke-NUS Medical School, said there are a number of factors that influence transmission dynamics and epidemics.

A surge could be caused by a change in the virus serotype.

There are four dengue viral strains and getting infected by one does not protect a person from getting the other three.

In the early part of this year, the less frequently seen DenV-3 appeared to be gaining ascendancy and was believed to have caused the rise in infections, as few people here are immune to it. But it now seems to have given way to DenV-2, which is often the dominant strain here.

Prof Gubler speculated that "if virus serotype and herd immunity, mosquito population densities and human behaviour have been ruled out, I would guess that it is the strain of virus".

"It has been demonstrated on several occasions that small mutations in the virus combined with positive selection can lead to the emergence of strains of virus of any serotype that have greater epidemic potential."

Infections are expected to stay high for some months with the hot and wet weather making it easier for mosquitoes to breed.

From today, heavier penalties will be imposed on households, construction sites and town councils found to be breeding mosquitoes as part of enhanced measures to contain dengue infection.

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Environment