Prostitution and the risk of STDs and AIDS in Nigeria and Thailand*

Research on AIDS in sub-Saharan Africa is determined by the nature of the epidemic in that region. All evidence continues to show that, apart from vertical transmission from mother to child and some continuing infection from blood transfusions, it is almost entirely a heterosexually transmitted epidemic. Both patient histories and physical examinations rule out the possibility of any significant level of transmission through homosexual activities or intravenous drug use. This evidence is supported by the parity by sex of the infected persons. Because of the very slight chance of an infected person transmitting the disease to another during each sexual act if they are otherwise healthy, there clearly must be other special circumstances necessary to sustain a fully heterosexual epidemic. Several possible factors have been studied: unusually high levels of sexual activity outside marriage; unusually high recourse by men to prostitutes; an unusual level of other sexually transmitted diseases (STDs) which act as co-factors; lack of male circumcision. A factor in the epidemic which allows the testing of the hypotheses is the fact that levels of the disease are much lower in most of West Africa (the exception being CTMte d'Ivoire) than they are in much of East and Southern Africa. After a dozen years of the epidemic this contrast can no longer be explained by diffusion from an original source. Research seems to show that the level of non-marital sexual activity, particularly by males, is high but no higher in East than West Africa or in some other populations outside Africa (Orubuloye et al. 1994). The focus of this non-marital sex on prostitutes is probably greater, at least in some of the larger cities, in East than West Africa but it is doubtful whether the margin is sufficient to explain the contrasting levels of the epidemic. There is probably a different incidence in the probable co-factors, with perhaps no differences in the overall levels of sexually transmitted diseases (STDs), but with East and Southern Africa displaying a higher incidence of the most likely co-factors, genital ulcerating diseases (GUDs), especially chancroid. This leaves us not only with the question of why there is a higher incidence of AIDS in parts of East and Southern Africa, but why there is a high level of chancroid. The answer may well be that these are the parts of the continent where males