Type A Flu requires a scientific definition. According to the Center for Disease Control and Prevention, “Influenza A viruses are divided into subtypes by two proteins on the surface of the virus: hemagglutinin (HA) and neuraminidase (NA)." There are 18 identified HA subtypes of the flu virus and 11 NA subtypes. The virus mixes these subtypes and proteins for easy and efficient mutations. The flexibility of the viral structure is what makes this type particularly dangerous for humans and other mammals. Type B and Type C flu are less capable of mutating.

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