A tropical disease is an illness that is most common or is limited to tropical or subtropical areas. These areas are characterized by high temperatures and humidity, which are often necessary for the disease-causing organism (vector) or their animal hosts to live. Depending on the disease, it may occur throughout the year, in relation to seasonal climatic changes or at irregular intervals. Outbreaks of these diseases may also occur outside tropical areas but tend to be sporadic.

More than two dozen illnesses may be classified as tropical diseases. They are diverse and linked more by where they occur than any other factor. They are caused by a variety of organisms, including viruses (e.g., dengue fever), bacteria (e.g., cholera, typhoid fever), protozoa (e.g., malaria, African sleeping sickness) and parasitic worms (e.g., schistosomiasis, filariasis). These organisms may be transmitted through various means, including insect bites, contaminated foods and environmental exposure.

While residents of areas where these diseases are endemic tend to be at highest risk, travelers to the region may also be infected. Several methods are available to reduce the chance of developing a tropical disease. Before the trip, the traveler is encouraged to gather information about current disease outbreaks from the U.S. Centers for Disease Control and Prevention (CDC) and World Health Organization (WHO). Patients should also contact their physician for appropriate vaccines or other prophylactic measures, such as medications. Insect and tick bites, which are potential routes of transmission, may be prevented by wearing long sleeves and pants and applying insect repellent to exposed skin. Thoroughly cooking foods and boiling water kills bacteria and may help prevent cholera, typhoid fever and other foodborne or water-related illnesses.

The tropical diseases cause a wide variety of symptoms that can range from mild to life threatening. In the early stages of disease many resemble symptoms of the flu but may quickly become severe. Travelers who develop symptoms, even within a year after traveling, should consult their physician and discuss the areas visited.

A tropical disease may be suspected based on the patient’s symptoms and travel history, but tests may be required for confirmation. These tests often require blood, urine, stool or tissue samples. In some instances, laboratory testing may be required, such as viewing the organism under a microscope.