The Indian Ocean paradox revisited: HIV and sexually transmitted infections in the Comoros.

The combination of high sexually transmitted infection (STI) prevalence and low HIV prevalence has been described as the Indian Ocean paradox. To investigate current epidemiology of HIV and STI in the Comoros, we conducted cross-sectional surveys of a representative sample of the adult population, and convenience samples of female sex workers and male STI patients. Only one (0.025%) of 3990 community participants was HIV-infected, while 142 (3.6%) had treponemal antibodies. Treponemal antibodies were not associated with past genital ulcers, number of sexual partners or adverse outcomes of pregnancies; their prevalence did not increase with age and there was no concordance within couples. Thus, most individuals with treponemal antibodies were probably infected during childhood with a non-venereal treponematosis. Only 1/70 (1.4%) and 0/83 sex workers sampled in 2004 and 2005 were HIV-infected. The Comoros have been protected by their insular status, male circumcision and paucity of syphilis. HIV control should focus on sex workers.