H1N1 (swine) influenza The H1N1 virus (swine flu) was a new flu
virus strain that caused a worldwide pandemic in humans from
June 2009 to August 2010. The Centers for Disease Control and
Prevention now call the virus 2009 H1N1. Causes, incidence, and
risk factors Earlier forms of the H1N1 virus were found in pigs.
Over time, the virus changed (mutated) and infected humans. H1N1
was a new virus in humans in 2009, and it spread quickly around
the world. Most of the people who got the H1N1 flu were ages 5 -
24. During the 2010-2011 flu season, H1N1 virus (swine flu) did
not cause widespread infections as it had in 2009-2010. The
2010-2011 seasonal flu vaccine also protected against swine flu,
and a separate vaccine was not needed. The same is true for the
2011-2012 seasonal flu vaccine Any flu virus can spread from
person to person when: - Someone with the flu coughs or sneezes
into air that others breathe in. - Someone touches a doorknob,
desk, computer, or counter with the H1N1 germs on it and then
touches the