influenza pandemic influenza pandemic an influenza pandemic is an epidemic of an influenza virus that spreads across a large region (either multiple continents or worldwide) and infects a large proportion of the population. there have been six major influenza epidemics in the last 140 years, with the 1918 flu pandemic being the most severe; this is estimated to have been responsible for the deaths of 50–100 million people. the most recent, the 2009 swine flu pandemic, resulted in under 300,000 deaths and is considered relatively mild. these pandemics occur irregularly. influenza (flu) types avian a/h5n1 subtype canine equine swine a/h1n1 subtype vaccines 2009 pandemic pandemrix live attenuated seasonal flu vaccine brands treatment amantadine baloxavir marboxil laninamivir oseltamivir peramivir rimantadine umifenovir zanamivir pandemics 1889-1890 russian flu 1918 spanish flu 1957-1958 asian flu 1968 hong kong flu 1977 russian flu 2009 swine flu outbreaks 1976 swine flu 2006 h5n1 india 2007 australian equine 2007 bernard matthews h5n1 2008 west bengal 2015 united states h5n2 outbreak 2020–2022 h5n8 outbreak