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Definition
By Mayo Clinic staffTechnically, the term swine flu refers to influenza in pigs. Occasionally, pigs transmit influenza viruses to people, mainly to hog farm workers and veterinarians. Less often, someone infected occupationally passes the infection to others.
The human respiratory infection caused by the influenza virus H1N1 — popularly known as swine flu — was first recognized in spring 2009, near the end of the usual Northern Hemisphere flu season.
A few months after the first cases of swine flu were reported, rates of confirmed H1N1-related illness were increasing in almost all parts of the world. As a result, the World Health Organization declared the infection a global pandemic. That official designation remained in place for more than a year, until the pandemic was declared over in August 2010. Currently, H1N1 is still circulating in humans as a seasonal flu virus and is included in the seasonal flu vaccine.
Another strain of swine flu — H3N2 variant — has also made its way into humans. This flu contains a gene from the H1N1 virus. So far, the virus has only been transmitted through human exposure to swine, not from human to human.
- Thorner AR. Epidemiology of pandemic H1N1 influenza ('swine influenza'). http://www.uptodate.com/index. Accessed May 10, 2012.
- H1N1 (Originally referred to as Swine Flu). U.S. Department of Health and Human Services. http://www.flu.gov/types/h1n1/index.html. Accessed May 10, 2012.
- Key facts about human infections with variant viruses (swine origin influenza viruses in humans). Centers for Disease Control and Prevention. http://www.cdc.gov/flu/swineflu/keyfacts-variant.htm. Accessed May 10, 2012.
- What you should know about antiviral drugs. Centers for Disease Control and Prevention. http://www.cdc.gov/flu/antivirals/whatyoushould.htm. Accessed May 10, 2012.
- Thorner AR. Clinical manifestations and diagnosis of pandemic H1N1 influenza ('swine influenza'). http://www.uptodate.com/index. Accessed May 10, 2012.
- Thorner AR. Treatment and prevention of pandemic H1N1 influenza ('swine influenza'). http://www.uptodate.com/index. Accessed May 10, 2012.
- Jefferson T, et al. Neuraminidase inhibitors for preventing and treating influenza in healthy adults and children. Cochrane Database of Systematic Reviews. http://ovidsp.tx.ovid.com/sp-3.5.1a/ovidweb.cgi?&S=MJGAFPPDAFDDBDDBNCALFHGCMLDJAA00&Complete+Reference=S.sh.15%7c1%7c1. Accessed May 10, 2012.
- The flu: What to do if you get sick. Centers for Disease Control and Prevention. http://www.cdc.gov/flu/takingcare.htm. Accessed May 10, 2012.
- Key facts about seasonal flu vaccine. Centers for Disease Control and Prevention. http://www.cdc.gov/flu/protect/keyfacts.htm. Accessed May 10, 2012.
- Vaccine selection for the 2011-2012 and 2012-2013 influenza seasons. Centers for Disease Control and Prevention. http://www.cdc.gov/flu/about/qa/vaccine-selection.htm. Accessed May 12, 2012.
- A guide to safe use of pain medicine. U.S. Food and Drug Administration. http://www.fda.gov/ForConsumers/ConsumerUpdates/ucm095673.htm. Accessed June 5, 2012.
- CDC reports cases 18-29 of H3N2v virus infection; continues to recommend interim precautions when interacting with pigs. Centers for Disease Control and Prevention. http://www.cdc.gov/flu/spotlights/h3n2v_us_cases.htm. Accessed Aug. 6, 2012.
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