and 9 types of Neuraminidases are known, giving rise to 144 combinations of the subtypes of influenza A virus. Common examples are H1N1, H3N2 ( Swine flu ) and H5N1 (bird/avian flu). All these subtypes infect and spread widely among humans resulting into pandemics. Tags: AntiViral , H1N1 , H3N2 , H5M1