Sexually transmitted diseases in mobile populations.

Introduction STDs and travel: an ancient association Sexually transmitted diseases have been associated with travel, and indeed blamed on travellers (particularly foreigners) since they were first described. The history of syphilis in Europe illustrates this well. Within two or three years of its first description in Naples, the disease had apparently spread to virtually every corner of Europe, transported presumably not only by the returning mercenary army of King Charles VIII of France, but also by camp followers, traders, sailors, pilgrims and other mobile populations. The variety of names given to the new disease reflects the perception that it was introduced by foreign travellers. The French called it the "mal de Naples", the Italians the "morbus gallicus" (French disease), the English called it the "French pox", and so on.' The study of, and clinical services for sexually transmitted diseases (STDs) were for many years the province of military and naval doctors, reflecting the high incidence of these diseases among mobile male populations; but the unique role of the armed forces in the dissemination of STDs has now been eclipsed by the extraordinary increase in international travel by civil populations in the past 50 years. Tourism is now the world's biggest industry. In 1993, UK residents made 36 million visits to foreign countries, and 19 million foreigners visited this country. Thirty million UK citizens visited Western Europe, three million North America and three million the rest of the world, including some 700 000 to subSaharan Africa.2 Although the vast majority of international travellers are holiday makers, the UN High Commission for Refugees estimates that there are at least 20 million refugees in the world who have fled from their countries of origin, and the International Labour Organisation states that there are some 30 million migrant workers3; the role played by such longer-term travellers in the transmission of STDs may be disproportionately large. The incidence and prevalence of many STDs varies greatly from one country to another, reflecting demographic, socioeconomic and cultural differences, and variation in the accessibility of effective treatment and of condoms. For example, the incidence of gonorrhoea in many European countries is now well below 100 per 100 000 total population per year, whereas the incidence in certain African countries is believed to be over 5000 per 100 000.4 The higher incidence and prevalence of the treatable bacterial STDs, particularly those such as chancroid and syphilis which cause genital ulceration, probably explains why there is a heterosexual HIV/AIDS epidemic in sub-Saharan Africa but not in Western Europe. People travelling from low prevalence regions to countries where over 10% of the adult population are HIV positive may not be aware of the enormously increased risk of exposing themselves to infection through casual heterosexual contact. This review will consider what is known about STDs in three mobile populations: international travellers from Europe, migrant workers in Southern Africa, and Rwandan refugees in camps in Tanzania; and will assess the possible options for STD control among these different categories of traveller.