Influenza Surveillance Under the Shadow of COVID-19 Pandemic: Phylogenetic Analysis of Influenza A (H1N1)pdm09 Viruses in Türkiye in 2019-20 Season

Introduction: Influenza is a severe health problem with a massive burden of disease mainly affecting older adults, young children, and people with multimorbidity. Global Influenza Hospital Surveillance Network (GIHSN) is an active hospital surveillance network that generates solid epidemiological and medical evidence to understand influenza severity and related risk factors and support vaccine strain selection. We aimed to analyze the data from the GIHSN Project 2019-20 - Türkiye to link clinical and viral data to infer potential viral genomic risk factors in hospitalized influenza patients and to get an overview of the genetic characterization of circulating influenza viruses in this cohort. Materials and Methods: This epidemiological active surveillance study followed the GIHSN core protocol and was conducted between the 51 st week of 2019 and the 18 th week of 2020. Cite