H7N9 is a bird flu strain of the species Influenza virus A ( avian influenza virus or bird flu virus ) .

Avian influenza A H7 viruses normally circulate Dispersal amongst avian populations with some variants known Know to occasionally infect humans .

As of January 2014 , there has been no evidence of sustained human-to-human transmission ; however , a study group headed by one of the world ’ s leading experts on avian flu reported Reporting that several instances of human-to-human infection are suspected Suspicion .