Revealing HIV epidemic dynamics and contrasting responses in two WHO Eastern European countries: insights from modeling and data triangulation.

Objectives: In the early 2000s, Estonia and Latvia experienced a rapidly growing HIV epidemic among people who inject drugs (PWID), and had, with Russia, the highest diagnosis rates in Europe. Understanding epidemic dynamics in both countries and how responses to HIV impacted them is essential to ending injection-driven epidemics.

Design: Statistical modeling, programmatic data collection, and triangulation.

Methods: Data on newly diagnosed HIV cases were used in a back-calculation model to estimate, for each country, trends in HIV incidence, time to diagnosis, and undiagnosed infections. Modeled estimates were then triangulated with programmatic data on harm reduction services, HIV testing, and ART.

Results: From 2007 to 2016, HIV incidence decreased in Estonia by 61% overall, for all exposure groups, and particularly for male PWID (97%), except men who have sex with men, where it increased by 418%. In Latvia, it increased by 72% overall. Median time to diagnosis decreased for male PWID in Estonia, from 3.5 to 2.6 years, but not in Latvia. In 2016, most new and undiagnosed infections, ∼50% in Latvia and ∼75% in Estonia, affected individuals reporting heterosexual transmission, showing a gradual shift toward heterosexual route as the main reported exposure mode. Coverage of services had been higher in Estonia; for example, by 2016, for PWID, there were >200 needles and syringes distributed per PWID annually, and HIV testing and ART coverage reached ∼50% and 76%, respectively, in Estonia, against respectively less than 100%, 10% and 27% in Latvia.

Conclusions: Estonia has turned the tide of its epidemic - large scale-up of prevention and care programs probably contributed to it - whereas in Latvia it remains very active.