For Example: A/Moscow/10/99(H3N2):

A = type of virus with A the most virulent of A, B or C

Moscow = the place where the specific strain was first isolated

10 = the 10th flu virus isolated in that particular year (in Moscow)

99 = the year in which it was isolated

H3 = indicating a specific surface protein, namely hemagglutinin3. There are 15 different hemagglutinin molecules, but only the first three appear to be found in human influenza viruses. All of the 15 hemagglutinin molecules, including for example H5, are associated with bird influenza viruses.

N2 = neuraminidase2, indicating a specific surface protein. There are nine different neuraminidase molecules, but only the first three appear to be found in human influenza viruses. Again, all nine neuraminidase molecules are associated with bird influenza viruses.

Reviewed (2006) by Dr Jane Yeats MBChB, BSc(Med)(Hons)Biochem, FCPathSA(Virology).