With all the talk about H1N1 influenza, I think it;s important for folks to understand where the H1 and N1 come from.
The "H" comes from the substance hemagglutinin and the "N" comes from neuraminidase. There have been identified influenza strains of the H and N types and this is how some influenza viruses are classified. The particular "swine" flu that has garnered so much attention is of the H1N1 type. A few years ago, the fear was of the avian type, H5N1.
This past Spring, the Wall Street Journal Health Blog did a good job explaining some of the background regarding the naming of this particular strain of influenza.
This may help us all understand the nomenclature and rationale behind what has become household names.