What is the H1N1 Virus (swine flu)?
H1N1 (also called swine flu, pig flu, and hog flu and is referred to as "swine flu" early on) is a new type of influenza virus causing illness in humans. This new type of virus was first detected in people in the United States in April 2009. Other countries, including Mexico and Canada, have reported people sick with this new virus. This virus spreads from person-to-person, probably in much the same way that a regular seasonal influenza viruses spread.
A swine influenza virus (SIV) is any strain of the influenza family of viruses that is usually hosted by
(is endemic in) pigs.
Why is the H1N1 virus sometimes called "swine flu"?
This virus was originally referred to as the "swine flu" because laboratory tests showed that many of the genes in this new virus were very similar to the influenza viruses that normally occur in pigs in North America. But further study has shown that this new virus is very different from what normally circulates in the North American pigs. It has two genes from flu viruses that normally circulate in pigs in Europe and Asia and avian genes and human genes. Scientists call this a "quadruple reassortant" virus.
