" Swine influenza or swine flu (commonly misspelled swine flue) refers to a range of influenza cases that are caused by viruses endemic to pigs. Swine flu infects some people every year, typically those in close contact with pigs. "
For a longer term view, see Wikipedia, which tells us:
Swine influenza virus (referred to as SIV) refers to influenza cases that are caused by Orthomyxoviruses endemic to pig populations.
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