Viruses known or likely to express M42.

20,245 sequences available on the NCBI database were analysed on Oct 10th, 2011, with a repeat search for new sequences of the form AG/GU on July 2nd 2012. The table excludes duplicate sequences, PR8 vaccine reassortants and over 50 cases where supposedly unique sequences showed phylogenetically implausible levels of similarity to PR8 or WSN, suggestive of mistakes in data curation or laboratory contamination of virus stocks.aHighly pathogenic avian influenza virus, by the molecular definition of possessing a polybasic HA cleavage site.bChange from AG/GCU SD sequence seen after virus adapted to replicate in mice.cMouse adapted virus but original virus sequence not available.