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H1N1 influenza (Swine flu)

The H1N1 virus (swine flu) is an infection of the nose, throat, and lungs. It is caused by the H1N1 influenza virus.

Causes

Earlier forms of the H1N1 virus were found in pigs (swine). Over time, the virus changed (mutated) and infected humans. H1N1 is a new virus first detected in humans in 2009. It spread quickly around the world.

During the 2010-2010 flu season, the H1N1 virus has not caused widespread infections. A separate vaccine has not been needed, though the H1N1 virus is still one of the three viruses included in the regular (seasonal) vaccine. 

You cannot get H1N1 flu virus from eating pork or any other food, drinking water, swimming in pools, or using hot tubs or saunas.

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 flu virus on it and then touches their mouth, eyes, or nose.
  • Someone touches mucus while taking care of a child or adult who is ill with the flu.

Alternative Names

Swine flu; H1N1 type A influenza

References

Centers for Disease Control and Prevention. Advisory Committee on Immunization Practices (ACIP) Recommended Immunization Schedules for Persons Aged 0 Through 18 Years and Adults Aged 19 Years and Older — United States, 2013. MMWR. 2013;62(Suppl1):1-19.

Dawood FS, Subbarao K, Fiore AE. Influenza viruses. In Long S, ed. Principles and Practice of Pediatric Infectious Diseases. 4th ed. Philadelphia, Pa.: Elsevier Saunders; 2012:chap 229.

Update Date: 4/16/2013

Updated by: C. Benjamin Ma, MD, Assistant Professor, Chief, Sports Medicine and Shoulder Service, UCSF Department of Orthopaedic Surgery. Also reviewed by A.D.A.M. Health Solutions, Ebix, Inc., Editorial Team: David Zieve, MD, MHA, Bethanne Black, Stephanie Slon, and Nissi Wang.

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