Co-circulation of pandemic 2009 H1N1, classical swine H1N1 and avian-like swine H1N1 influenza viruses in pigs in China

► The pandemic 2009 A/H1N1 influenza viruses emerged in pigs in China. ► The endemic H1N1 swine influenza viruses were isolated from pigs in China. ► Multiple lineages of H1N1 influenza viruses are currently co-circulating in the swine population.