Molecular Epidemiology of Influenza A (H5N6) Viruses from Human Infections in Jiangsu Province, China

Background Human infections with avian influenza A (H5N6) have been reported with increasing frequency in recent years. This study aims to systematically characterize the epidemiological and molecular characteristics of human H5N6 infections in Jiangsu Province, China, in order to inform epidemic prevention and control strategies and support clinical diagnosis. Methods Human cases of H5N6 infections were collected in Jiangsu Province. Clinical and epidemiological data of the cases were investigated and analyzed. Phylogenetic and evolutionary analyses were performed using the Jiangsu-derived viral strains together with publicly available reference sequences, employing MEGA and BEAST, and R packages. Results Between November 2018 and the present, five laboratory-confirmed human cases of avian influenza A (H5N6) infection were reported in Jiangsu Province. The ages of the patients ranged from 6 to 81 years. All close contacts tested negative for H5N6 nucleic acid. Environmental investigations revealed only one sample positive for H5N6 nucleic acid. Phylogenetic analysis showed that all hemagglutination genes clustered within evolutionary branch 2.3.4.4h and 2.3.4.4b. The median time to the most recent common ancestor of the Jiangsu viruses was estimated to be December 2009 for the HA gene and July 2014 for the neuraminidase gene. Conclusions This study provides a comprehensive overview of the epidemiological and molecular characteristics of human H5N6 infections in Jiangsu Province. No evidence of human-to-human transmission was found among the infected cases and their close contacts. However, the ongoing genetic evolution of H5N6 viruses may increase the risk of human infection and warrants continued surveillance.