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Swine flu strain with pandemic potential increasingly found in Chinese pigs

A new flu virus found in Chinese pigs has become more infectious to humans and needs to be watched closely in case it becomes a potential “pandemic virus”, according to a study published by the U.S. journal, Proceedings of the National Academy of Sciences {PNAS}; although experts said there is no imminent threat. A team of Chinese researchers looked at influenza viruses found in pigs from 2011 to 2018 and found a “G4” strain of H1N1 that has “all the essential hallmarks of a candidate pandemic virus,” according to the paper. The virus is a unique blend of three lineages: one similar to strains found in European and Asian birds, the H1N1 strain that caused the 2009 pandemic, and a North American H1N1 that has genes from avian, human, and pig influenza viruses. The variant is especially concerning because its core is an avian influenza virus—to which humans have no immunity—with bits of mammalian strains mixed in. As part of a project to identify potential pandemic influenza strains, a team led by Liu Jinhua from the China Agricultural University analysed nearly 30,000 nasal swabs taken from pigs at slaughterhouses in 10 Chinese provinces, and another 1,000 swabs from pigs with respiratory symptoms seen at their school’s veterinary teaching hospital. The swabs, collected between 2011 and 2018, yielded 179 swine influenza viruses, the vast majority of which were G4 or one of five other G strains from the Eurasian avian like lineage. “G4 virus has shown a sharp increase since 2016, and is the predominant genotype in circulation in pigs detected across at least 10 provinces,” they write.