HIV-2 continues to decrease, whereas HIV-1 is stabilizing in Guinea-Bissau

OBJECTIVE: Although Guinea-Bissau has the world's highest prevalence of HIV-2, it has been decreasing since 1987. Meanwhile, the prevalence of HIV-1 has been increasing. We describe both the prevalence and changes in incidence of HIV-2 and HIV-1 during the last 30 years of observation in the capital Bissau in Guinea-Bissau. METHODS: A total of 3125 adults living in 412 houses in Bissau were eligible for inclusion in the present cross-sectional survey conducted from November 2014 to February 2016. All participants had a questionnaire filled out and a blood sample taken. Results were compared with previous surveys. RESULTS: Of the 3125 eligible adults, 2601 (83.2%) individuals participated. The overall prevalence of HIV decreased from 8.6% (218/2548) in 2006 to 6.7% (173/2601) in 2016 with an age-adjusted and sex-adjusted prevalence ratio (aPR) of 0.71 [95% confidence interval (CI) = 0.59-0.85]. Including HIV-1/2 dual infections, a decrease in the overall prevalence of HIV-2 from 4.4% (112/2548) to 2.8% (72/2601) was observed with an aPR of 0.55 (95% CI = 0.41-0.73). The overall prevalence of HIV-1 decreased from 4.6% (118/2548) to 4% (104/2601) with an aPR of 0.81 (95% CI = 0.63-1.05). Incidence rates for HIV-2 and HIV-1, estimated for 815 individuals, decreased from 0.24 to 0.09 and from 0.50 to 0.40 per 100 person-years of observation, respectively, in the periods between 1996-2006 and 2006-2016. CONCLUSION: The prevalence of HIV-2 continues to decrease, whereas the prevalence of HIV-1 showed sign of stabilization. The results observed may be explained by a lower pathogenicity of HIV-2 and changes in risk behavior.