Dengue infections in Singapore at 16-year low, with no deaths in first nine months

In the first 50 weeks of the year, 2,629 people had dengue - a drop of more than 10,000 from the same period last year.
In the first 50 weeks of the year, 2,629 people had dengue - a drop of more than 10,000 from the same period last year.PHOTO: REUTERS

SINGAPORE - Dengue infections this year have fallen to their lowest level in 16 years.

In the first 50 weeks of the year, 2,629 people had dengue - a drop of more than 10,000 from the same period last year.

Though there are still two weeks to go before the end of the year, the total number of infections for 2017 is likely to be lower than any in the past 16 years. There were 2,372 cases in 2001.

The drop is in stark contrast to the 13,100 people infected last year - and the all-time high of more than 22,000 infections in 2013.

There was no dengue death in the January to September period. Last year, nine people died, including a 11-year-old boy. Generally, one in five people with dengue ends up in hospital.

However, the drop in infections is not due to better control of mosquito breeding. In fact, the National Environment Agency (NEA) said it is catching more Aedes mosquitoes under its surveillance system.

An NEA spokesman said this suggests "an increased number of the mosquito vector in our community".

She added that the low number of infections this year is probably because the dominant viral strain is DENV-2, which many people here have immunity against.

There are four dengue strains. Once someone has been infected, he is protected against that strain, but not the other three strains.

DENV-2 was also the dominant strain last year, as well as between 2007 and 2012. As a result, many people who were previously infected are now immune to that strain.

The NEA spokesman warned that despite the huge drop in infections this year, the danger of it flaring up again remains.

"Dengue transmission is a complex interplay of many factors, such as the mosquito population, virus type, human immunity and environmental parameters such as temperature, rainfall and humidity," she said. 

As so many factors cannot be controlled, she added, efforts must continue to keep the mosquito population down, since it is through mosquito bites that the viral infection is transmitted.

The last quarterly surveillance data also showed a drop in DENV-2 infections - from 69 per cent of all infections in August to 38 per cent in September.

A change in the dominant strain could lead to a surge in infections as fewer people might be immune.

There are now four active dengue clusters: two adjoining ones in Bedok Reservoir Road with a total of 62 cases, one in Toa Payoh Lorong 2 with three reported cases, and one in Tampines Street 21 with two infections.