Dodging Mosquito-Borne Diseases

Malaria, dengue fever, Japanese encephalitis, yellow fever, chikungunya, West Nile and other unpleasant diseases are mosquito-borne. The WHO estimates that, each year, there are:
•    390 million cases of dengue (2015)
•    198 million cases of malaria (2013)
•    200 thousand cases of yellow fever (2014)
•    68 thousand cases of Japanese encephalitis (2014)

Those are big numbers. Travelers need to be alert to health risks from mosquito bites in some parts of the world, but mosquito borne diseases can be avoided.

Who Has the Most Dangerous Mosquitoes?

You might not know you've been bitten by a mosquito
until you become ill. User: Ngari.norway CC BY-SA 3.0

Mosquito bites in North America, Europe, northern Asia and most of Australia are unwelcome but usually not considered life threatening. They’re painful, itchy, and can become infected, and the sound of a bloodthirsty mosquito whining around your head can drive you mad. Mosquito-borne diseases, however, aren’t usually a big concern. In recent years, a slight risk of contracting West Nile virus has heightened the level of concern about mosquito bites in North America.

In the tropics, it’s different. Mosquito bites can be deadly. Day flying mosquitoes transmit dengue fever and yellow fever: the night flyers bring malaria and Japanese encephalitis. Some locations as well as some seasons mean higher risk. Be careful. The first line of defense is to know the enemy – travelers should take time, before they go, to find out what the risks are at their destination.

Preventing Mosquito-Bourne Diseases

Travelers can be immunized against yellow fever and Japanese encephalitis, and antimalarial drugs are advised to prevent malaria, but none of these work 100 percent of the time, and there’s no protection against dengue or chikungunya. The only way to be sure you don’t catch any of the mosquito borne diseases is to be sure you don’t get any mosquito bites. It’s not as easy as you might think.

A trip to Southeast Asia – my first trip to a destination where mosquitoes were a particular concern – taught me many useful things:

•    Even in the dry season, there are mosquitoes virtually everywhere you go; I saw my first Asian mosquito in the taxi from the Bangkok airport.

•    Many hotels and guest houses do not have intact window screens and tight doors – mosquitoes get in through grates, tears in screens, and under doors. Perhaps this shouldn’t have surprised me, but it did.

•    Mosquito bed netting often isn’t provided either. Mosquito bed netting is indispensable, preferably netting that has been soaked in mosquito repellent. Buy it at home and take it with you. Don’t assume there will be a hook available to hang bed netting – carry a hook that can be screwed into wood and a long piece of cord that you can stretch across a room, say from a curtain rod to a closet rod or some other fixture. You may have to get creative.

•    Don’t expect the local people to warn you about mosquitoes or help you take precautions. Their level of concern can be surprisingly low and they may deny the presence of mosquitoes even when you have just seen one checking out your ankles.

•    Bring lots of mosquito repellent with a minimum concentration of 30% DEET (check recommendations for children). This can be hard to find in Asian shops, though, surprisingly, we had better luck in the small markets used by local people than in the shops aimed at tourists. Remember that insect repellent is only effective for a certain number of hours and will be removed by swimming, sweating, and showering. Carry repellent with you and reapply it diligently – at a minimum, morning and evening.

•    Light colored clothing is recommended, as well as long sleeves and long pants or skirts. Don’t be too quick to rule out the more extensive clothing – long sleeved shirts and pants made of light cotton can be surprisingly cool and they’ll protect you from both insects and sunburn.

I got through my Southeast Asian vacation without any mosquito bites that I was aware of, though one black fly did sample my blood in northern Thailand. I say “that I was aware of” because I found the mosquitoes in Thailand, Cambodia and Laos to be both smaller and quieter than the ones I’m used to; if you don’t react to the bite you might never know you had a visitor.