pandemic severity index pandemic severity index the pandemic severity index (psi) was a proposed classification scale for reporting the severity of influenza pandemics in the united states. the psi was accompanied by a set of guidelines intended to help communicate appropriate actions for communities to follow in potential pandemic situations. released by the united states department of health and human services (hhs) on february 1, 2007, the psi was designed to resemble the saffir-simpson hurricane scale classification scheme. the index was replaced by the pandemic severity assessment framework in 2014, which uses quadrants based on transmissibility and clinical severity rather than a linear scale. 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