Since the advent of air travel, people more frequently visit these regions and contract many of these diseases, most notably malaria and hepatitis. Any nontropical condition however should never be overlooked in those returning from the tropics.

Diseases

The Special Programme for Research and Training in Tropical Diseases (TDR) of the World Health Organization focuses on neglected infectious diseases that disproportionally affect poor and marginalized populations. The current disease portfolio includes the following ten:

• African trypanosomiasis
• Dengue fever
• Leishmaniasis
• Malaria
• Schistosomiasis
• Tuberculosis
• Chagas disease
• Leprosy
• Lymphatic filariasis
• Onchocerciasis

Although leprosy and tuberculosis are not exclusively tropical diseases (they have occurred everywhere), their highest incidence in the tropics justify its inclusion. Cholera and yellow fever also fall into this category.

Some tropical diseases are very rare, but may occur in sudden epidemics, such as the Ebola hemorrhagic fever, Lassa fever and the Marburg virus. There are hundreds of different tropical diseases which are less known or rarer, but that, nonetheless, have importance for public health, such as:

• Oropouche virus
• Lobomycosis
• West Nile disease
• Lábrea fever
• Rocio disease
• Mapucho hemorrhagic fever
• Trachoma
• Guinea worm
• Chikungunya
• etc.

Relation of climate to tropical diseases

The proliferation of so-called "exotic" diseases in the tropics has long been noted both by travellers and explorers, as well as by physicians. One obvious reason is that the hot climate present during all the year and the larger volume of rains directly affect the formation of breeding grounds, the larger number and variety of natural reservoirs and animal diseases that can be transmitted to humans (zoonosis), the largest number of possible insect vectors of diseases. It is possible also that higher temperatures may favour the replication of pathogenic agents both inside and outside biological organisms. Socio-economic factors may be also in operation, since most of the poorest nations of the world are in the tropics. Tropical countries like Brazil, which have improved their socio-economic situation and invested in hygiene, public health and the combat of transmissible diseases have achieved dramatic results in relation to the elimination or decrease of many endemic tropical diseases in their territory.

The greenhouse effect and the increasing global temperature of the atmosphere seem to be influencing the spread of tropical diseases and vectors to other latitudes that were previously spared them, such as the Southern United States, the Mediterran area, etc.