Jung M. auteur aut IRD Leye N. auteur aut IRD Vidal Nicole auteur aut IRD Fargette Denis auteur aut IRD Diop H. auteur aut IRD Kane C. T. auteur aut IRD Gascuel O. auteur aut IRD Peeters Martine auteur aut IRD text journalArticle eng text/pdf reformatted digital access Background: The classification of HIV-1 strains in subtypes and Circulating Recombinant Forms (CRFs) has helped in tracking the course of the HIV pandemic. In Senegal, which is located at the tip of West Africa, CRF02_AG predominates in the general population and Female Sex Workers (FSWs). In contrast, 40% of Men having Sex with Men (MSM) in Senegal are infected with subtype C. In this study we analyzed the geographical origins and introduction dates of HIV-1 C in Senegal in order to better understand the evolutionary history of this subtype, which predominates today in the MSM population Methodology/Principal Findings: We used a combination of phylogenetic analyses and a Bayesian coalescent-based approach, to study the phylogenetic relationships in pol of 56 subtype C isolates from Senegal with 3,025 subtype C strains that were sampled worldwide. Our analysis shows a significantly well supported cluster which contains all subtype C strains that circulate among MSM in Senegal. The MSM cluster and other strains from Senegal are widely dispersed among the different subclusters of African HIV-1 C strains, suggesting multiple introductions of subtype C in Senegal from many different southern and east African countries. More detailed analyses show that HIV-1 C strains from MSM are more closely related to those from southern Africa. The estimated date of the MRCA of subtype C in the MSM population in Senegal is estimated to be in the early 80's. Conclusions/Significance: Our evolutionary reconstructions suggest that multiple subtype C viruses with a common ancestor originating in the early 1970s entered Senegal. There was only one efficient spread in the MSM population, which most likely resulted from a single introduction, underlining the importance of high-risk behavior in spread of viruses. specialized SENEGAL 052 7 3 e33579 2012 1932-6203 https://www.documentation.ird.fr/hor/fdi:010055928 10.1371/journal.pone.0033579 1932-6203 [F B010055928] https://www.documentation.ird.fr/hor/fdi:010055928 https://horizon.documentation.ird.fr/exl-doc/pleins_textes/divers17-09/010055928.pdf IRD - Base Horizon / Pleins textes 2012-07-04 2017-10-03 fdi:010055928 fre