from Ars Technica:
Swine flu, bird flu, H1N1—tracking the influenza virus can be a confusing task, not generally made easier by the fact that most people only attempt to do so when addled by flu symptoms or in the midst of worries about a potential pandemic. We recognize that the latter appears to apply to the current situation, but we'll do our part to try to explain a bit of the biology of the virus. Putting together this explanation was made a bit challenging by the fact that anyone we could find who has detailed knowledge of the influenza virus appears to be busy actually working on the current outbreak.
On the surface: the HxNx nomenclature
Like most viruses, the currently spreading swine flu virus has a coat formed of proteins which surround the genetic material that allows the virus to hijack a cell and reproduce. These coat proteins are critical in a variety of ways: they determine which cells the virus can latch onto and infect and, being exposed, they're the things that antibodies recognize when your body generates an immune response to the virus. For the flu virus, the major coat proteins are called hemagglutinin and neuraminidase—the H and N of the commonly used nomenclature for identifying these viruses.
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