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What is H1N1 (swine flu)? H1N1 (referred to as ęswine fluę early on) is a new influenza virus causing illness in people. This new virus was first detected in people in April 2009 in the United States. Other countries, including Mexico and Canada, have reported people sick with this new virus. This virus is spreading from person-to-person, probably in much the same way that regular seasonal influenza viruses spread. Why is this new H1N1 virus sometimes called "swine flu"? This virus was originally referred to as "swine flu" because laboratory testing showed that many of the genes in this new virus were very similar to 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 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. Taken from: http://www.cdc.gov/h1n1flu/swineflu_you.htm