Background STI prevalence or incidence data among HIV infected can help to distinguish populations with different levels of sexual HIV transmission risk. Herpes simplex virus type 2 (HSV-2) is considered useful because it is almost exclusively sexually transmitted, cannot be cured and leads to the production of lifelong antibodies. Unfortunately, few IDU studies include HSV-2 prevalence data.

Aim of the current work is to examine prevalence of and associations between HSV-2 infection, and HIV infection among injecting drug users (IDUs) in Kohtla-Järve, Estonia.

Methods Current IDU were recruited using chain referral methodology (RDS). Informed consent was obtained, a structured questionnaire including demographics, drug use history, and sexual risk behaviour was administered, and a blood sample was collected for HIV and HSV-2 antibody testing.

Results A total of 600 subjects were recruited in 2012. Subjects were primarily male (73%), with a mean age of 30 (SD 4.9) years. The prevalences of HIV and HSV-2 were 62%, and 32%, accordingly. Odds for being HSV-2 positive was higher among HIV infected IDUs (OR 1.9.95% CI 1.3–2.9). One third (27%) of the sexually active IDUs reported always using condoms (with in the last 4 weeks) prior the study.

Being HSV-2 positive was not associated with reported injection risk behaviour. HSV-2 seropositivity was associated with gender (higher among women; OR 2.7, 95% CI 1.8–4.0), and sexual behaviour: higher among those reporting IDU-sexual partners (OR 1.7, 95% CI 1.1–2.7), and those not always using condom (OR 2.0, 95% CI 1.2–3.4).

Conclusion HSV-2 seroprevalence can be used as a marker of (long-term) sexual risk. However, it might not capture more recent behaviour change in response to the HIV/AIDS among population groups studied.

High prevalence of HSV2 infection coupled with low reported condom use highlight the need of targeted sexual risk reduction interventions for IDU and their partners.