Settings for identifying recent HIV infections: the Portuguese experience

Portugal has been the western European country with the highest rate of notified acquired immunodeficiency syndrome (AIDS) cases since 1999 and human immunodeficiency virus (HIV) infection cases since 2000. Nonetheless, exact information on the magnitude and trends of recently acquired infections is missing. In a cross-sectional study we aimed to determine HIV prevalence, the proportion of recently acquired infections and the incidence among patients attending a Sexually Transmitted Infections (STI) clinic and among HIV positive cases tested at the AIDS Reference Laboratory (ARL), by using the Avidity Index (AI) of antibodies to identify recent HIV-1 seroconversions. Demographic and behavioural data were collected. At the STI clinic 253 patients were enrolled, 16 were found to be HIV infected (14 HIV-1, 2 HIV-2) and a prevalence of 6.3% was obtained. Four recent HIV-1 infections were identified and the HIV-1 incidence was 3.3% per year. At the ARL, 332 newly diagnosed cases of HIV-1 infection were studied, 59 (17.8%) were recent infections and an annual incidence of 4.1% was estimated. These findings support STI clinics as key sentinel sites for recently acquired HIV infections and illustrate the viability of testing for recent HIV infections in these settings and reinforce the value of this method in the surveillance for better monitoring current trends of the HIV/AIDS epidemic in Portugal.