If you are also using a sunscreen the sunscreen should be applied first to allow it to bind to the skin. Subsequent application of insect repellent will decrease the effectiveness of the sunscreen by about a third. Malaria tablets will be prescribed for travellers to endemic areas in addition to the avoidance measures. Yellow fever virus is transmitted by Aedes mosquitoes in tropical South America and Africa, and a vaccine is available. Many countries require a yellow fever vaccination certificate if travellers have come from a WHO-designated infected area.
Dengue fever is found throughout the tropics and is also due to a virus spread via mosquitoes.
They resemble our native deerflies. These crawling insects bite exposed faces and other skin areas while the traveller sleeps at night. They prefer thatched roof huts and adobe buildings where there are cracks to hide. Avoid such shelters in favour of insect-proof tents, jungle hammocks or the like. Wearing footwear and restriction of swimming to salt water or chlorinated pools will avert these hazards.