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

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.