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. These insects may carry a parasite, bacterium or virus that is infectious to humans and animals.
Click on any of the tropical diseases in the sidebar for more information about that particular disease.
African Trypanosomiasis, also known as “sleeping sickness,” is caused by microscopic parasites of the species Trypanosoma brucei. It is transmitted by the tsetse fly (Glossina species), which is found only in rural Africa. Although the infection is not found in the United States, historically, it has been a serious public health problem in some regions of sub-Saharan Africa. Currently, about 10,000 new cases each year are reported to the World Health organization; however, it is believed that many cases go undiagnosed and unreported. Sleeping sickness is curable with medication, but is fatal if left untreated.
Chagas disease is named after the Brazilian physician Carlos Chagas, who discovered the disease in 1909. It is caused by the parasite Trypanosoma cruzi, which is transmitted to animals and people by insect vectors that are found only in the Americas (mainly, in rural areas of Latin America where poverty is widespread). Chagas disease (T. cruzi infection) is also referred to as American trypanosomiasis.
In the United States, Chagas disease is considered a Neglected Infection of Poverty (NIP) since it is found mostly in those with limited resources and limited access to medical care.
With more than one-third of the world’s population living in areas at risk for transmission, dengue infection is a leading cause of illness and death in the tropics and subtropics. As many as 100 million people are infected yearly. Dengue is caused by any one of four related viruses transmitted by mosquitoes. There are not yet any vaccines to prevent infection with dengue virus (DENV) and the most effective protective measures are those that avoid mosquito bites. When infected, early recognition and prompt supportive treatment can substantially lower the risk of developing severe disease.
Dengue has emerged as a worldwide problem only since the 1950s. Although dengue rarely occurs in the continental United States, it is endemic in Puerto Rico, and in many popular tourist destinations in Latin America and Southeast Asia; periodic outbreaks occur in Samoa and Guam.
Soil-transmitted helminths refer to the intestinal worms infecting humans that are transmitted through contaminated soil (“helminth” means parasitic worm): Ascaris lumbricoides (sometimes called just “Ascaris“), whipworm (Trichuris trichiura), and hookworm (Anclostoma duodenale and Necator americanus). A large part of the world’s population is infected with one or more of these soil-transmitted helminths:
- approximately 807-1,121 million with Ascaris
- approximately 604-795 million with whipworm
- approximately 576-740 million with hookworm
Leishmaniasis includes two major diseases, cutaneous leishmaniasis and visceral leishmaniasis, caused by more than 20 different leishmanial species.
Cutaneous leishmaniasis, the most common form of the disease, causes skin ulcers. Visceral leishmaniasis causes a severe systemic disease that is usually fatal without treatment. Mucocutaneous leishmaniasis is a rare but severe form affecting the nasal and oral mucosa.
Leishmaniasis is transmitted by the bite of small insects called sand flies. Many leishmanial species infect animals as well as humans. The distribution is worldwide, but 90% of visceral leishmaniasis cases occur in India, Bangladesh, Nepal, Sudan, Ethiopia and Brazil, while 90% of cutaneous leishmaniasis cases occur in Afghanistan, Algeria, Iran, Saudi Arabia, Syria, Brazil, Colombia, Peru and Bolivia.
This chronic infectious disease usually affects the skin and peripheral nerves but has a wide range of possible clinical manifestations. Patients are classified as having paucibacillary or multibacillary Hansen’s disease. Paucibacillary Hansen’s disease is milder and characterized by one or more hypopigmented skin macules. Multibacillary Hansen’s disease is associated with symmetric skin lesions, nodules, plaques, thickened dermis, and frequent involvement of the nasal mucosa resulting in nasal congestion and epistaxis.
Lymphatic filariasis, considered globally as a Neglected Tropical Disease, is a parasitic disease caused by microscopic, thread-like worms. The adult worms only live in the human lymph system. The lymph system maintains the body’s fluid balance and fights infections. Lymphatic filariasis is spread from person to person by mosquitoes.
People with the disease can suffer from lymphedema and elephantiasis and in men, swelling of the scrotum, called hydrocele. Lymphatic filariasis is a leading cause of permanent disability worldwide. Communities frequently shun and reject women and men disfigured by the disease. Affected people frequently are unable to work because of their disability, and this harms their families and their communities.
Malaria is a mosquito-borne disease caused by a parasite. People with malaria often experience fever, chills, and flu-like illness. Left untreated, they may develop severe complications and die. In 2008, an estimated 190 – 311 million cases of malaria occurred worldwide and 708,000 – 1,003,000 people died, most of them young children in sub-Saharan Africa.
Onchocerciasis, or River Blindness, is a Neglected Tropical Disease (NTD) caused by the parasitic worm Onchocerca volvulus. It is transmitted through repeated bites by blackflies of the genus Simulium. The disease is called River Blindness because the blackfly that transmits the infection lives and breeds near fast-flowing streams and rivers and the infection can result in blindness. In addition to visual impairment or blindness, onchocerciasis causes skin disease, including nodules under the skin or debilitating itching. Worldwide onchocerciasis is second only to trachoma as an infectious cause of blindness.\
Schistosomiasis, also known as bilharzia, is a disease caused by parasitic worms. Although the worms that cause schistosomiasis are not found in the United States, more than 200 million people are infected worldwide. In terms of impact this disease is second only to malaria as the most devastating parasitic disease. Schistosomiasis is considered one of the Neglected Tropical Diseases (NTDs).
The parasites that cause schistosomiasis live in certain types of freshwater snails. The infectious form of the parasite, known as cercariae, emerge from the snail, hence contaminating water. You can become infected when your skin comes in contact with contaminated freshwater. Most human infections are caused by Schistosoma mansoni, S. haematobium, or S. japonicum.
In spite of fewer people in this country suffering from TB, it remains a serious threat, especially for HIV-infected persons. In fact, worldwide TB is one of the leading causes of death among people infected with HIV.
People infected with HIV (the virus that causes AIDS) are more likely than uninfected people to get sick with other infections and diseases. TB is one of these diseases.
Tuberculosis (TB) is a disease caused by a bacterium called Mycobacterium tuberculosis. The bacteria usually attack the lungs, but TB bacteria can attack any part of the body such as the kidney, spine, and brain. If not treated properly, TB disease can be fatal. TB disease was once the leading cause of death in the United States.