Jun 13, 2013

    Don't believe all you hear on dengue

    With over 9,500 cases of dengue reported this year, Singapore's battle against the epidemic rages on.

    However, old wives' tales of mosquitoes and dengue, such as treating the virus by drinking papaya-leaf juice, remain pervasive.

    My Paper gets Dr Ng Lee Ching, director of the Environmental Health Institute, to sort out fact from fiction.


    Does the Aedes mosquito not bite at night?


    The Aedes mosquitoes' peak biting period is at dawn and dusk, but they will also bite during other times of the day.


    In Singapore, due to artificial lights like white lights in homes, we will see them biting at night.


    Is the Aedes mosquito attracted to people with certain blood types?


    There are scanty studies showing that people with blood type O are more prone to getting bitten, but it is not an established fact.



    Do dark-coloured clothes attract Aedes mosquitoes?


    Mosquitoes are attracted to dark colours. Also, (clothing of) dark colours retains body heat, and they are attracted to heat.


    They are also attracted to carbon dioxide, and, hence, our breath. Some of the traps in our studies used carbon dioxide to attract mosquitoes.


    Am I less susceptible if I live in a high-rise flat or apartment, because the Aedes mosquito cannot fly above a certain height?


    Our studies have shown that mosquitoes can fly all the way up to the 21st floor.



    Are people with smelly feet more prone to getting bitten by the Aedes mosquito?


    Smelly feet has never been shown to attract the Aedes aegypti species, but it has been shown to attract the Anopheles mosquito, which transmits malaria.



    Will keeping certain types of plants help to ward off mosquitoes?


    Certain types of plants like citronella and neem are shown to repel mosquitoes, but only within a small area. You can't assume that by putting one of these plants at home, the mosquitoes will all fly out.



    If I drop a paracetamol tablet into the water in my flower vase, will mosquitoes not be able to breed there?


    I have never heard of this myth, but you could try putting salt, chlorine or detergent, as long as it does not kill your plant. We advocate the use of the insecticide Bti.

    Can drinking papaya-leaf juice help to treat dengue?

    There is no evidence to show that this works. The best advice is to go to the doctor.

    Are my chances of getting bitten by mosquitoes and contracting dengue higher in forested areas?

    The Aedes aegypti species is not typically found in the forest.

    However, the Aedes albopictus species is and can transmit dengue, but it is not a good vector.

    The aegypti species is commonly found in an urban setting.