HIV-1 subtype diversity in Europe

Although subtype B historically dominated HIV-1 epidemics in western and parts of central Europe, the WHO European region is now characterised by a heterogeneous mixture of HIV-1 variants including non-B subtypes, circulating recombinant forms (CRFs), and unique recombinant forms. This diversification reflects repeated introductions through migration, local onward transmission, and ongoing recombination. Subtype A, particularly sub-subtype A6, continues to dominate much of eastern Europe, where the largest regional burden of HIV-1 is concentrated. Across Europe, marked regional differences persist, with subtype B remaining common in western Europe, diverse non-B variants and CRFs contributing to western and central European epidemics, and recombinant forms increasingly recognised across all regions. Emerging clinical and laboratory data suggest that sub-subtype A6 might have an increased propensity to develop resistance under cabotegravir pressure, with potential implications for long-acting cabotegravir-rilpivirine treatment and cabotegravir-based pre-exposure prophylaxis in regions where A6 circulates widely. Subtype diversity might also affect virulence, reservoir dynamics, and susceptibility to broadly neutralising antibodies and other novel therapeutic approaches. In this Review, we summarise the changing epidemiology of HIV-1 variants in Europe and outline how growing viral diversity should inform prevention, treatment, and surveillance strategies.