Next-Gen sequencing of novel pandemic swine flu [A(H1N1)pdm09] virus in India revealed novel mutations across the genome

The Influenza A H1N1 virus of 2009 was the first pandemic flu virus of the 21st century. Identifying the emergence of mutations in rapidly mutating Influenza viruses that allow increased transmission or confer resistance are invaluable to global outbreak response. Here we recovered 5 complete Influenza A genomes from 4 oropharygeal swabs and one cell culture isolate from a severe Indian outbreak of flu in early 2015. Multiple amino acids substitutions including those known to confer resistance to Oseltamivir and increased pathogenecity in mice were found in the Neuraminidase gene. Additional mutations both reported and novel were found throughout the genome compared to the vaccine strain (California/04/2009). All eight segments of the complete genomes were found to be genetically related to the 2009 pandemic strain, A(H1N1)pdm09 and belonging to the emerging genogroup 6B. This group was found to be of south East Asian origin by time scale phylogentic analysis. A phylogeographic analysis revealed 39 significant migration events among globally circulating viruses. This study is the first extensive complete genome and phylogeographic analysis of 2015 Indian A(H1N1) pdm09 viruses. We report several novel mutations in the 2015 Indian strains which need to be evaluated for effect on viral replication, transmission and resistance to therapy. The identification of mutant A(H1N1)pdm09 from India warrants continuous monitoring of viral evolution for implementation of suitable medical countermeasures.