HIV-1 subtype B spread through cross-border clusters in the Balkans: a molecular analysis in view of incidence trends.

Objectives: To analyze phylogenetic relations and assess the role of cross-border clusters in the spread of HIV-1 subtype B across the Balkans, given the general trends of new HIV diagnoses in seven Balkan countries.

Design: Retrospective phylogenetic and trend analysis.

Methods: In-depth phylogenetic, phylodynamic and phylogeographic analysis performed on 2415 HIV-1 subtype B sequences from 1999 to 2019 using maximal likelihood and Bayesian methods.