<unk>  influenza usually occurs in outbreaks/pandemics, and the incidence may vary greatly from one year to another. The 2009 H1N1 global infection rate was 11% to 21%. During the 2009<unk>  influenza outbreak, the incidence in the USA was approximately 18,000 per 100,000 individuals (a total of 60 million cases) with approximately 265,000 hospitalizations reported. The worldwide case fatality rate is unknown, but is thought to range from 15,000 (initial reports) to 500,000 when patients with no healthcare access were counted. Individuals of all age groups may be affected by<unk>  influenza. There is no gender or racial predilection to the development of<unk>  influenza.
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