Molecular detection and characterization of Influenza 'C' viruses from western India.

Since 2003, India has had a well-established influenza surveillance network, though Influenza C virus was not the focus of study. We therefore retrospectively analyzed clinical samples from Pune, western India collected during January 2009 to August 2015, by real-time RT-PCR. Three of 2530 samples of patients with influenza-like illness (ILI) or severe acute respiratory illness (SARI) showed positivity for Influenza C virus infection, while 105 and 31 samples were positive for Influenza A and B viruses respectively. Influenza C viruses were successfully isolated using the embryonated egg system and whole genomes were sequenced and analyzed phylogenetically. HE gene-based phylogeny showed that two viruses C/India/P119564/2011 and C/India P121719/2012 clustered with the C/Sao Paulo/378/82 (SP82) lineage, whereas C/India/P135047/2013 clustered with the C/Kanagawa/1/76 (KA76) lineage. The internal gene of these viruses grouped in two lineages. The PB1, PB2, M and NS genes of the study viruses grouped with C/Yamagata/26/81 (YA81), while the P3 (PA) and NP genes grouped with C/Mississippi/80 (MS80). Bayesian clock studies conclude that the Indian strains may have emerged through multiple reassortment events.