Tropical diseases are
diseases that are prevalent in or unique to
tropical and
subtropical regions. The diseases are less prevalent in
temperate climates, due in part to the occurrence of a cold
season, which controls the insect population by forcing hibernation. Insects such as mosquitoes and flies are by far the most common disease carrier, or
vector. These insects may carry a parasite, bacterium or virus that is infectious to humans and animals. Most often disease is transmitted by an insect "bite", which causes transmission of the infectious agent through subcutaneous blood exchange. Vaccines are not available for most of the diseases listed here, and many do not have cures.