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askST: What is the risk of dengue at nature areas compared to residential areas?

Reader Stella Ng Sze Hwei wrote to askST: "What is the risk of dengue at parks and hiking places like MacRitchie Reservoir compared to residential areas?"

Environment reporter Audrey Tan checked with the National Environment Agency.

There is a smaller risk of contracting dengue in the green spaces here, compared to urban spaces. But low risk does not mean no risk.

The National Environment Agency (NEA) says 140 species of mosquitos have been found in Singapore. But only two of them - Aedes aegypti and Aedes albopictus - can transmit dengue here.

Of the two, Aedes albopictus is commonly found in forests, parks and areas with much greenery, but it is not as efficient as transmitting dengue as Aedes aegypti, which thrives in urban areas.

Still, the NEA cautioned that Aedes albopictus has been responsible for outbreaks overseas when present in large numbers in densely populated areas.

"There is therefore some risk of acquiring dengue through this mosquito in our green spaces, particularly those with higher human traffic. However, the risk is comparatively lower than that in residential areas," said an NEA spokesman.

As for the Aedes aegypti, it has adapted to living in close proximity to humans and thrives in urban areas with a preference of biting humans. It usually breeds in artificial or natural water containers or bodies, including containers, flower pots or trays.

Said the NEA spokesman: "The risk of dengue is higher in areas with high human congregation such as urban residential areas, including parks and playgrounds... where there is higher likelihood of finding Aedes aegypti and infected humans, as compared to forested areas."

She noted that while it is common to detect dengue virus in mosquitoes from residential areas, no dengue virus has been detected amongst the tens of thousands of mosquitoes collected from forested areas.

Dengue cases are on the rise here. More cases were reported in the last week of April, as compared to the week before, according to figures from NEA's dengue website.

 

There was a total of 244 cases reported from April 24 to 30 - an increase of 15 cases from the previous week.

On the back of this increase, staying protected from mozzie bites should be a priority at home or when venturing outdoors.

The NEA spokesman advised members of the public to protect themselves from mosquito bites when visiting Singapore's nature areas by applying insect repellent and wearing long-sleeved, loose fitting and light coloured clothing.

Products containing DEET (N,N-diethyl-m-toluamide) or picaridin as the active ingredient are generally most effective in repelling mosquitoes, she added. These are usually more effective against biting insects compared to products using natural or plant-based insect repellent oil such as citronella, lemongrass or eucalyptus.

The dengue risk can also be removed at home by performing the 5-step Mozzie Wipeout, which includes steps such as overturning unused water storage containers. More details of this can be found on NEA's website.

audreyt@sph.com.sg

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