Tropical medicine has been notoriously difficult to define because so few illnesses are limited to the tropics, and so many are found there. Be that as itmay, tropical medicine is concerned mainly with a number of parasitic and other infectious diseases that are responsible for major health problems in low-income tropical countries. For example, malaria causes one million deaths per year, mostly in children under five in Africa. In certain villages of Zaireand Angola, trypanosomiasis (sleeping sickness) affects 70-80% of inhabitants. Leprosy is synonymous with stigma, and new treatment regimens offer hope that it will soon be controlled. But it still afflicts between one and two million people in the world, mostly in Asia, Africa, and Latin America. Fifteenmillion poor people in 73 countries suffer from gross enlargement of the limbs, a symptom of chronic filarial disease.
Many of these so-called tropical diseases also existed in Europe and North America until relatively recently. In the Middle Ages leprosy was epidemic throughout Europe, and malaria was endemic in swampy regions in the United Statesand Europe into the 20th century. In the summer of 1793 an epidemic of yellow fever forced the United States government to relocate from Philadelphia toNew York. Although other conditions, like epilepsy, can occur anywhere, in the tropics they are found at a higher rate as a result of parasitic infections. In addition, the changing epidemiology of diseases such as polio, now undercontrol in temperate climates, emphasizes their importance in the tropics.
Tropical medicine as a discipline was established by colonial powers, mainlyEngland, France, and the Netherlands, to protect their citizens in the colonies; it was essentially colonial medicine. Later, tropical medicine became concerned with the health of local populations in the tropics. This trend increased dramatically with the independence of the former colonies in the 1960s. Travel medicine, a branch of tropical medicine, continues the focus on the health of outsiders visiting the tropics. International health considers the broader questions that concern populations of the tropics, focusing on health and development, rather than the treatment of individual cases of particular diseases. Clinical tropical medicine is a subspecialty of infectious diseases dealing with selected parasitic and fewer bacterial (e.g., leprosy) and viral(e.g., yellow fever) pathogens. Outside tropical regions, clinical tropical medicine is mainly the concern of travel medicine and infectious disease specialists. Within the tropics, tropical medicine is for the most part indistinguishable from general medicine.
Research efforts in tropical medicine comprise both basic and applied research. Basic research concentrates on pathogens and vectors -- that is, organismsthat carry infectious agents from one host to another -- in the disciplinesof immunology, molecular biology, and other biological life sciences. Appliedresearch aims to generate drugs, vaccines, and other approaches to treatmentand prevention. Because of the respective level of investment required and anticipated returns, it is easier to find support for basic research than applied research for most tropical diseases. Whereas basic research yields important contributions to science, applied research requires major inputs that areless likely to earn financial rewards for investors from the impoverished affected populations.
Current priorities in tropical medicine and international health are focusedon control or eradication (where possible) of tropical diseases with three basic approaches: (1) better treatments for clinical tropical medicine (e.g., drugs and surgery); (2) disease-specific public health interventions (e.g., vaccines, vector control, insected-impregnated bednets to kill the mosquitoes that carry malaria, and so on); and (3) general development efforts to reducethe burden of tropical diseases (e.g., sanitation, hygiene, and decreasing poverty). These last measures were most effective in eliminating tropical diseases from Europe and North America.
Although the role of "tropical medicine" as it is traditionally understood ispresently the subject of a lively debate, an argument could be made for itsviability on the following grounds: It continues to provide a focus on majordiseases of low-income countries that would otherwise be neglected because applied research lacks commercial potential. Tropical diseases are closely linked to problems of international health and needs for general development. Inthe overall scope of the discipline, the initial focus on the health of outsiders is now less of a priority.