You are probably aware that all flus have names like H5N1 or H3N2. That is because every flu virus has two types of proteins on its surface—hemagglutinin and neuraminidase—and these account for the H and N in their names. H5N1 means that the virus combines the fifth known iteration of hemagglutinin with the first known iteration of neuraminidase, and for some reason that is a particularly nasty combination.
