What do the numbers and letters mean?

[Solstice Goat]

Did you ever wonder what�s going on with all those viruses and the numbers attached to them? Since everyone at the U.S. CDC/FDA seems to be gearing up for a new pandemic virus out of China, the H7N9, perhaps we ought to become acquainted with the numerous strains of viruses.

First, what do the letters in a virus �name� represent, i.e., the �H� and the �N�? Both represent glycoproteins HA and NA, which are hemagglutinin and neuraminidase, spike-like protrusions on the flu virus surface, which are responsible for attachment and �invasion�.

There is quite a roster of glycoproteins: 16 HAs and 9 NAs that can or may have the same hosts. However, we have to keep in mind that influenza viruses also have type classifications, viz., A, B, and C. Type C is the mildest; B, which primarily infects humans, can be a real �sickie� but it will never produce type A, which is the pandemic strain.

Now to a listing of glycoproteins, which may be helpful in understanding virus �speak�.

H1, H2, N1, and N2 have the same hosts: humans, pigs, birds

H4, H5, H6, H8, H10 through H16 all have the same host: birds

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