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HIV epidemic and needs beyond fast-track cities: a transmission networks analysis to study the dynamic of HIV clusters in a French region near Paris

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Feb 24, 2026 version files 1.83 MB

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Abstract

The Centre-Loire Valley region is a low-density demographic and medical region near the fast-track city of Paris, with persistent elevated rate of positive HIV testing. We investigated the role and characteristics of transmission clusters in the HIV dynamics in this region for appropriate local response. HIV pol gene sequences collected in Centre-Loire Valley over a decade (2010-2020) were included in a phylogenetic analysis combined with epidemiological data. Putative transmission clusters were inferred using HIV TRACE methods. Risk factors of being part of a cluster were studied using multivariate logistic regression models. Of the 1305 participants, 579 (44%) were born out of France, mainly from Sub-Saharan Africa, 494 (38%) were women, 433 (33%) men who have sex with men (MSM), 694 (53%) heterosexuals. Migrants had lower CD4 cell count at diagnosis than those born in France (296 vs 443, p< 0.01), likely due to delayed time to diagnosis. A total of 86 clusters were identified (clustering rate of 21%) including 33 of size ≥ 3 involving 170 participants (3-16 per cluster). MSM (OR 2.16, p< 0.01) and higher viral load (OR 1.21, p< 0.01) were risk factors of clustering. Individuals born abroad were at lower risk than those born in France (OR 0.03, p < 0.01). Among large clusters, persistent virological control was achieved in a median of 75% of participants vs 83% outside clusters (p<0.01). Molecular epidemiology showed that MSM were part of local transmission networks but not heterosexual migrants, suggesting distinct epidemic features and needs.