Circulation of HIV-1 A6 variant in the East border of European Union - dynamics of the virus transmissions between Poland and Ukraine

BACKGROUND

The Human Immunodeficiency Virus-1 (HIV-1) A6 variant is dominating in high-prevalence Eastern European countries with increasing prevalence over the remaining regions of Europe. The recent war in Ukraine may contribute to further introductions of this A6 lineage. Our aim was to model the transmission dynamics of the HIV-1 A6 variant between Poland and Ukraine.

METHODS

HIV-1 A6 partial pol sequences originating from Poland (n=1,185) and Ukraine (n=653) were combined with publicly available sequences (n=7,675) from 37 other countries. We used maximum likelihood-based tree estimation followed by a Bayesian inference strategy to characterize the putative transmission clades. Asymmetric discrete phylogeographic analysis was used to identify the best-supported virus migration events across administrative regions of Poland and Ukraine.

RESULTS

We identified 206 clades (n=1,362 sequences) circulating in Poland or Ukraine (63 binational, 79 exclusively Polish and containing only 64 Ukrainian sequences). Cross-border migrations were almost exclusively unidirectional (from Ukraine to Poland, 99.4%), mainly from East and South Ukraine (Donetsk - 49.7% and Odessa - 17.6% regions) to Central (Masovian - 67.3%, Lodz - 18.2%), and Western Pomeranian (10.1%) districts of Poland. The primary sources of viral dispersal were the Eastern regions of Ukraine, long-time affected by armed conflict and large population centers in Poland.

CONCLUSIONS

The Polish outbreak of the A6 epidemic was fueled by complex viral migration patterns across the country, together with cross-border transmissions from Ukraine. There is an urgent need to include war-displaced people in the national HIV prevention and treatment programs to reduce the further spread of transmission networks.