Background HIV and herpes simplex virus type-2 (HSV-2) are infections transmitted predominantly through sexual intercourse. We explored the ecological association between the prevalence of HIV and HSV-2 among human populations through a global review.

Methods We conducted a global systematic literature review of HIV and HSV-2 prevalence following the PRISMA guidelines. Sources of data used were Medline (PubMed) and Embase databases, and several country-level reports. No language, country, or year limitations were imposed. We included any publication with a serological measurement of HIV and HSV-2 prevalence in the same study population.

Results A total of 2,927 records were screened. Based on preliminary descriptive analysis, we found that HIV prevalence increased steadily with HSV-2 prevalence in all populations where the dominant mode of transmission was sexual. HSV-2 prevalence was consistently larger than HIV prevalence. Overall, among high-risk populations, both infections prevalence was high. Among general population groups, HIV prevalence varied across settings, but was correlated with HSV-2 prevalence, which also varied widely. Though HIV and HSV-2 prevalence levels were correlated across populations, there were settings with very low HIV prevalence regardless of HSV-2 prevalence. For children and injecting drug users where the dominant mode of HIV transmission was not sexual, there was no apparent ecological association between the two infections.

Conclusions Our findings support a strong ecological association between HIV and HSV-2 prevalence in all populations where the dominant mode of HIV transmission is sexual. Sexual networks conducive of HSV-2 transmission appear to be also conducive of HIV transmission. Further analytical work is needed to quantify the ecological association between the two infections, to determine whether HSV-2 could be predictive of HIV epidemic potential, and to assess whether there is a threshold of HSV-2 prevalence necessary for a sexual network to be sustainable for HIV transmission besides HSV-2 transmission.