The flu is not just one virus, but is acually many diffent strains that are all made up diffrently. The flu virus is broken up first by type, A, B, and C. A is the one we will be worrying about in this section. The A type of influenza is split up into strains.Each stain is named a name like H1N1 or H7N2. The H stands for hemagglutinin and the N stands for neuraminidase. Hemagglutinin is for attaching the virus to your cell and the neuraminidase is for realeaseing it.Each is a protein that can be found on the flu virus. In the name of the flu aslo contains a number after each letter. The number stands for a diffrent type of each protein. The H can be followed by a number 1 through 16 and the N can be followed by 1 through 9. In total this gives us 144 diffent combinations of the flu. Each has different characteristics and infects diffrent things. Below is a chart of the combinations of H and N and what they can infect. You can see that only some of them infect humans, and all of them can be found in waterfowl and birds. You can use the chart to see what the different strains infect. For example H6N2 will infect waterfowl like ducks, humans, and pigs.