Swine Flu
(Swine Influenza A [H1N1 and H3N2v] Virus)

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Swine flu (H1N1 and H3N2v influenza virus) facts

  • Swine flu is a respiratory disease caused by influenza viruses that infect the respiratory tract of pigs and result in a barking cough, decreased appetite, nasal secretions, and listless behavior.
  • Swine flu viruses may mutate (change) so that they are easily transmissible among humans.
  • The 2009 swine flu outbreak was due to infection with the so-called H1N1 virus and was first observed in Mexico.
  • Symptoms of swine flu in humans are similar to most influenza infections: fever (100 F or greater), cough, nasal secretions, fatigue, and headache.
  • Two antiviral agents, zanamivir (Relenza) and oseltamivir (Tamiflu), have been reported to help prevent or reduce the effects of swine flu if taken within 48 hours of the onset of symptoms.

What is swine flu?

Swine flu (swine influenza) is a respiratory disease caused by viruses (influenza viruses) that infect the respiratory tract of pigs, resulting in nasal secretions, a barking cough, decreased appetite, and listless behavior. Swine flu produces most of the same symptoms in pigs as human flu produces in people. Swine flu can last about one to two weeks in pigs that survive. Swine influenza virus was first isolated from pigs in 1930 in the U.S. and has been recognized by pork producers and veterinarians to cause infections in pigs worldwide. In a number of instances, people have developed the swine flu infection when they are closely associated with pigs (for example, farmers, pork processors), and likewise, pig populations have occasionally been infected with the human flu infection. In most instances, the cross-species infections (swine virus to man; human flu virus to pigs) have remained in local areas and have not caused national or worldwide infections in either pigs or humans. Unfortunately, this cross-species situation with influenza viruses has had the potential to change. Investigators decided the 2009 swine flu strain, first seen in Mexico, should be termed novel H1N1 flu since it was mainly found infecting people and exhibits two main surface antigens, H1 (hemagglutinin type 1) and N1 (neuraminidase type1). The eight RNA strands from novel H1N1 flu have one strand derived from human flu strains, two from avian (bird) strains, and five from swine strains. Swine flu is transmitted from person to person by inhalation or ingestion of droplets containing virus from people sneezing or coughing; it is not transmitted by eating cooked pork products. The newest swine flu virus that has caused swine flu is influenza A H3N2v (commonly termed H3N2v) that began as an outbreak in 2011. The "v" in the name means the virus is a variant that normally infects only pigs but has begun to infect humans.

Medically Reviewed by a Doctor on 9/23/2013

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What to Do if You Think You Have H1N1 Swine Flu Virus

If you've got fever, cough, or one of the other symptoms of the flu, you may be wondering if you have contracted the H1N1 swine flu virus. The reality is that it isn't possible to know unless specialized testing is ordered, and for uncomplicated cases of the flu in non-hospitalized patients, routine testing for the H1N1 virus is not being carried out.

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