Influenzavirus A is a genus of a family of viruses called Orthomyxoviridae in virus classification. Influenzavirus A has only one species in it; that species is called "Influenza A virus". Influenza A virus causes "avian influenza" (also known as bird flu, avian flu, Influenzavirus A flu, type A flu, or genus A flu). It is hosted by birds, but may infect several species of mammals.
Influenzavirus A has many types of viruses,such as bird flu, human flu, swine flu, horse flu and dog flu.
And Human influenza virus also have different types, they ordered by the number of known human deaths- Slides
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