What is H1N1 (swine) flu?

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 United States in April 2009. 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.

Related H1N1 Flu Questions

• Why is this new H1N1 virus sometimes called “swine flu”?
• Are there human infections with H1N1 (swine) flu in the U.S.?
• How many H1N1 (swine) flu viruses are there?
• How serious is H1N1 (swine) flu infection?
• How severe is illness associated with this new H1N1 virus?
• Is this H1N1 (swine) flu virus contagious?
• What are the signs and symptoms of H1N1 (swine) flu in people?
• What is the difference between a vaccine and an antiviral?