Evolution of Clusters Transmission Patterns in France during the Last Decade

ABSTRACT

Background: The recent transmission clusters (RTCs) identified through phylogenetic approaches allow to describe the main transmission networks. This render possible to describe potential shifts among HIV transmission routes and populations and, in some cases, to specifically target prevention measures. Here we describe the evolution of RTCs over the last decade in a specialized laboratory serving centers from the entire French territory. Method(s) We extracted all the HIV reverse transcriptase sequences available between 01/01/2013 and 31/08/2022. The sequences dataset was studied overall and divided into three equal time periods 2013-15, 2016-18, 2019-2021. The first sequences available for each patient were aligned and the trees were reconstructed by maximum likelihood using IQtree software. Clusters, defined by a maximum genetic distance < 4.5% and a branch support >90%, were extracted using ClusterPicker. Result(s) Overall, 8591 sequences were included. Among them, 950 RTCs were identified including 2492 sequences (29%) and 68 large RTCs ( >4 sequences) with 475 (5.6%) sequences. The mean duration of large RTCs (from the first to the last sequences) was 5.1 years [IQR 4.1-7.1] and 34 were still active (including at least one sequence during the last year of the study period). 3640, 2897 and 2157 sequences were included for the 2013-15, 2016-18 and 2019-2021 periods, respectively. We identified 298 RTCs (19.5% of sequences), 249 (20.4%) and 226 (27.5%) among those periods, respectively. While the number of sequence pairs decreased from 2013-15 to 2019-21, the number of large RTCs increased steadily (see Table 1). During the period 2019-21, including the largest clusters, patients belonging to a RTC were more often male (68 vs 58%, p< 0.001) and younger (average age 39 vs 44 years, p< 0.001) than non-RTC patients. This observation was even more marked for very large RTCs (see Table 2). It should be noted that the largest cluster (14 patients) was mainly composed of women and located in French overseas territories. Conclusion(s) This study shows an evolution of the structure of HIV sequence clusters over time with a decreasing number of small RTCs but an increasing number of large RTCs. These trends can be explained by a better global control of transmission, due in part to TasP, but not preventing some super-transmitters networks, despite PrEP use and not only including MSM is some settings. The COVID period does not seem to have strongly prevented such large transmission networks.