What is flu notation?

Flu notaintion used to tell what kind of virus your dealing with. example- A/California/8/09/(H3N2)

The a at the beginning stand for what type of virus your dealing with (subtype a, b or c)

California means that this particular strain was first found and isolated in california.

The 8 stands for the 8th flu virus isolated in that particular year in california

09 tell the year the virus was first found- 2009

The H3N2 stands for the hemaggluton molecules (H) and the neuraminidase molecules(N). The first number next to the H states how many hemaggluton proteins there are (there are 15). Same with the neruominidase (there are only 9). In the neuraminidase case only the first three proteins (1,2,3) are known to infect humans.