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Swine influenza symptoms on swinehu.svg Illustration of antigenic shift Swineinfluenzasymptomsonswineen svg UTC Swineinfluenzasymptomsonswineen svg Swinevirus svg AntigenicShiftHiRes National Institute of Allergy and Infectious Diseases NIAID Original uploader was Zedla at org en Converted to by Fvasconcellos derivative