High circulation of Respiratory Syncytial Virus in pediatric patients hospitalized with severe acute respiratory infection in Senegal, 2022-2023.

<bold>Background:</bold> Acute respiratory infections caused by RSV can be severe, resulting in pediatric hospitalizations and childhood deaths, mostly in developing countries. So here, we investigated the epidemiology and the genetic characteristics of RSV infections among patients hospitalized with severe acute respiratory infections using data from the 2022-2023 sentinel surveillance. <bold>Methods:</bold> Nasopharyngeal swab samples were collected from hospitalized patients as part of the SARI surveillance in Senegal. A multiplex RT-PCR was used for the detection of respiratory pathogens, including RSV. Subsequently, a subset of RSV positive samples was randomly selected, to undergo whole genome sequencing for phylogenetic analysis. <bold>Results:</bold> Overall, 1570 samples were received and analyzed at the Senegalese NIC. Among enrolled patients, 54.8% were males, 45.2% were children aged under 1 year and children above 5 years represented 30%. RSV was detected in 14.6%, among which RSV-A was confirmed in 40.4% and RSV-B in 59.1%. RSV positivity was significantly higher in infants aged ≤11 months (58.3%) than in the other age groups and a co-circulation of both type of RSV during seasonal epidemic periods with alternating patterns of predominance over time was observed. Phylogenetic analyses revealed that all RSV-A strains belonged to GA2.3.5 genotype and all RSV-B strains to GB5.0.5a genotype. <bold>Conclusion:</bold> Our findings reveal a relatively high prevalence of RSV infection among hospitalized pediatric patients in Senegal with an exclusive co-circulation of two genetic lineages of RSV during seasonal epidemic with alternating patterns of predominance.