This explains the naming of viruses based upon H (hemagglutinin) groups and N (Neuraminidase) groups.

Most influenza in this era is H1N1 and H3N2.

Humans get Influenza A and B. Influenza A affects humans, but also birds and mammals. Influenza B affects humans and seals.



Because type A can affect birds and mammals, an influenza type A can jump species from a bird, affect a pig, which is a major concern since a pig has a very similar circultory sysytem (we actually used to use replacement heart valves from pigs), then pass the illness to a human.