Avian influenza A/H5N1, Avian influenza A/H7N9, and
Novel H1N1 influenza A
Influenza A virus subtype H5N1 has greater virulence, easier (more efficient) human-to-human transmission, and resistance to antiviral drugs, compared to seasonal influenza A viruses and other avian influenza viruses.
Novel H1N1 influenza A virus caused a pandemic in 2009.
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