Silhol R, Coupland H, Baggaley RF, et al. - This study’s findings demonstrate that herpes simplex virus type 2 (HSV-2) may have contributed to at least 37% of incident HIV infections in the past decade worldwide, and even more in Africa, and may continue to do so despite increased antiretroviral therapy (ART) access unless future improved HSV-2 control measures, such as vaccines, become available.

• The predicted transmission population-attributable fraction (tPAF) was 37.3% (95% uncertainty interval: 33.4%–43.2%), and an estimated 5.6 (4.5–7.0) million incident heterosexual HIV infections were due to HSV-2 globally over 2009–2018, under the conservative scenario.

• For the African region, the contribution of HSV-2 to HIV infections was largest [tPAF = 42.6% (38.0%–51.2%)] and was lowest for the European region [tPAF = 11.2% (7.9%–13.8%)].

• They found higher tPAF among female sex workers, their clients, and older populations, reflecting their higher HSV-2 prevalence.

• The results showed that tPAF was approximately 50% and 1.3- to 2.4-fold higher for the liberal or fully liberal scenario than the conservative scenario across regions.