Tropical diseases — diseases found in tropical and subtropical regions — annually infect hundreds of millions of people. These diseases are usually transmitted through the bites of mosquitoes or other insects. Without a winter to limit the insect population, infection rate remains constant throughout the year. The number of infections overall is on the rise due to the increased number of people moving in and out of tropical areas. Should infections occur despite preventive measures, many tropical diseases are curable.
A common and probably the most well-known tropical disease is malaria. Malaria is caused by a microorganism that enters the bloodstream through mosquito bites. Responsible for up to 3 million deaths per year, malaria causes high fever, vomiting, fatigue and enlargement of the spleen. Children with the disease are more likely than adults to suffer permanent brain damage. A variety of antimalarial drugs exist to prevent the disease.
Dengue fever, like malaria, falls into the category of tropical diseases contracted through mosquito bites. Unlike malaria, though, dengue fever is a viral infection. Besides rash, symptoms include headache, vomiting and extreme bodily pain. There is no vaccine or preventive treatment for dengue fever. Mosquito eradication efforts in tropical countries have had some success in limiting the number of cases.
Out of all tropical diseases, the Ebola virus has the highest mortality rate — 70-90% depending on the specific strain. Present only in central Africa, the virus is spread through contact with the bodily fluids of an infected person. Sporadic outbreaks since the mid-1970s have killed thousands of people. Symptoms are varied, but in fatal cases they always lead to multi-organ failure. Though recent research has shown promise, there is no approved vaccine.
Two diseases that are not tropical in nature but occur in high numbers in the tropics are leprosy and tuberculosis. These diseases are bacterial, and both spread through the air when an infected person coughs. Out of the two, tuberculosis is more highly contagious and kills faster. Several new vaccines are under development to prevent tuberculosis. There is no vaccine for leprosy.
Treating tropical diseases depends on the disease. Malaria, leprosy and tuberculosis all have approved treatment methods. The mortality rate rises the longer a patient waits before beginning treatment. As there is no treatment for the Ebola virus or dengue fever, the goal for a doctor is to keep patients stable until the disease runs its course. Due to the high mortality rate of both diseases, however, these efforts save very few lives.