Travel epidemiology--a global perspective.

In order to have a rational approach to necessary preventive measures it is essential to know the health risks. The 80 million travellers each year with destinations in Africa, Asia, Latin America, Pacific Islands and remote areas in Eastern Europe are exposed to a broad range of pathogens that are rarely encountered at home. The risk depends on the degree of endemicity in the area visited, the duration of stay, the individual behaviour and the preventive measures taken. Travellers' diarrhoea (TD) is the most frequent ailment of visitors to countries with poor hygiene. The incidence rate is 25-90% in the first 2 weeks abroad. The risk of TD is far less in travellers originating in a high risk country, as some immunity develops. Malaria is an important risk for travellers going to endemic areas. Without chemoprophylaxis, the monthly incidence is high in some destinations, among them frequently visited tropical Africa where 80-95% of the infections are due to Plasmodium falciparum. The incidence rates are lower in most endemic areas of Asia and Latin America where Plasmodium vivax predominates. The risk is nil in all capital cities of South America and SE Asia, as well as in many frequently visited tourist destinations. The diseases preventable by immunization will be discussed in a separate paper (Vaccination priorities; page 175). Sexually transmitted diseases occur frequently, as some travellers (5% of Europeans) engage in casual sex, approximately half of them without being protected by a condom. The prevalence for HIV-infection, syphilis, gonorrhoea, etc. often exceeds 50% in prostitutes. In some European countries, a major proportion of heterosexuals with newly acquired HIV-infection have acquired it while abroad.