Infectious diseases

There are many infectious diseases that can pose a hazard to travellers who may not be familiar with them and their risks, because they are rare or absent in their home countries. This article is a basic introduction to some of these hazards of travel, how to avoid them, and how to deal with one if you contract it. For those unfamiliar with medical jargon, the words infectious and contagious have distinct meanings. An infectious disease is one that is caused by a pathogen, such as a virus, bacterium, fungus or other parasites. A contagious disease is one that is easily transmitted by being in the vicinity of an infected person. All contagious diseases, such as influenza and measles, are infectious diseases, but the reverse is not necessarily true, with various diseases such as AIDS or yellow fever being infectious but not contagious.

Vast improvements in sanitation and healthcare standards, combined with the widespread availability of vaccines, have made many once common diseases largely a thing of the past in developed countries. However, these diseases may continue to persist in less developed parts of the world where people do not have access to proper medical care and sanitation, and vaccine coverage is low. Also, differences in climate often mean that both pathogens and their vectors (carriers which are usually pests, such as mosquitoes) are quite different. Local people have developed immunity to many of the local pathogens, but travellers will be vulnerable. Travellers' diarrhea is the commonest of these infections.