Prospective cohort study of female sex workers and the risk of HIV infection in Alicante, Spain (1986-96).

OBJECTIVE To measure the incidence of HIV infection over a 10 year follow up in a cohort of female commercial sex workers in Alicante (Spain), and to determine factors associated with high risk of infection. METHODS A prospective cohort study was carried in an AIDS information and prevention centre in Alicante, Spain. Of the 1388 female sex workers who initially sought the services of the centre since September 1986, 657 completed at least one additional follow up visit before December 1996. Main outcome measures were infection with HIV-1 and reported risk behaviours. RESULTS During 1815 person years of observation among 657 female sex workers who were free of HIV infection (negative test), 16 women developed of HIV infection (incidence rate of HIV infection = 8.8 cases/1000 woman years, 95% confidence interval (CI): 5.4-14.4). Reported current use of injecting drugs at the first visit was associated with an increased risk of HIV infection (relative risk, RR = 12.87, 95% CI: 4.81-34.15) as well as having an usual partner with injecting drug addiction (RR = 20.89, 95% CI: 7.44-58.70). Infection also was associated with younger age (RR for 1 year = 0.86, 95% CI: 0.76-0.96). After multivariate adjustment using Poisson regression analysis, the factors that remained significantly associated with the risk of HIV infection were current use of injecting drugs (RR = 4.61, 95% CI: 1.37-15.46), and having a usual partner with injecting drug addiction (RR = 10.08, 95% CI: 2.94-34.57). There was also some evidence that a younger age could be related to infection. CONCLUSION These data suggest that the risk of HIV infection among this cohort of female sex workers in Alicante is predominately associated with the use of injecting drugs, and having a regular partner with injecting drug addiction. An increasing number of clients did not play a role in the risk of infection.