Novel H1N1 (referred to as "swine flu" early on) is a new influenza virus causing illness in people. This new virus was first detected in people in the U.S. in April 2009. This virus is contagious and spreading from person-to-person worldwide, probably in much the same way that regular seasonal influenza viruses spread (through coughing or sneezing by people with influenza). On June 11, 2009, the World Health Organization (WHO) signaled that a pandemic of novel H1N1 flu was underway.
The 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 (swine) in North America. But further study has shown that this new virus is very different from what normally circulates in North American pigs.
Most people who have become ill with this virus have recovered without requiring medical treatment, although severe illnesses and death have occurred as a result of illness associated with it. (Source: CDC / Photo: Kaupang/iStockphoto)