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- Swine flu (H1N1 and H3N2v influenza virus) facts
- What is the swine flu?
- How is swine flu transmitted? Is swine flu contagious?
- What is the incubation period for swine flu?
- What is the contagious period for swine flu?
- How long does the swine flu last?
- What causes swine flu?
- Why is swine flu now infecting humans?
- What are swine flu symptoms and signs?
- What tests do health-care professionals use to diagnose swine flu?
- What types of doctors treat swine flu?
- What is the treatment for swine flu?
- What is the history of swine flu in humans?
- What are the risk factors for swine flu?
- Can swine flu be prevented with a vaccine?
- Can swine flu be prevented if the swine flu vaccine (or other flu strain vaccines) is not readily available?
- Are there home remedies for swine flu?
- Was swine flu (H1N1) a cause of an epidemic or pandemic in the 2009-2010 flu season?
- What is the prognosis (outlook) and complications for patients who get swine flu?
- Where can I find more information about swine flu (H1N1 and H3N2v)?
Quick GuideRespiratory Infections: Pneumonia, Bronchitis, Flu, and More
What is the history of swine flu in humans?
In 1976, there was an outbreak of swine flu at Fort Dix. This virus was not the same as the 2009 H1N1 outbreak, but it was similar insofar as it was an influenza A virus that had similarities to the swine flu virus. There was one death at Fort Dix. The government decided to produce a vaccine against this virus, but the vaccine was associated with rare instances of neurological complications (Guillain-Barré syndrome) and was discontinued. Some individuals speculate that formalin, used to inactivate the virus, may have played a role in the development of this complication in 1976. One of the reasons it takes a few months to develop a new vaccine is to test the vaccine for safety to avoid the complications seen in the 1976 vaccine. Individuals with active infections or diseases of the nervous system are also not recommended to get flu vaccines.
Early in the spring of 2009, H1N1 flu virus was first detected in Mexico, causing some deaths among a "younger" population. It began increasing during the summer 2009 and rapidly spread to the U.S. and to Europe and eventually worldwide. The WHO declared it first fit their criteria for an epidemic and then, in June 2009, the WHO declared the first flu pandemic in 41 years. There was a worldwide concern and people began to improve in hand washing and other prevention methods while they awaited vaccine development. The trivalent vaccine made for the 2009-2010 flu season offered virtually no protection from H1N1. New vaccines were developed (both live and killed virus) and started to become available in Sept. 2009-Oct. 2009. The CDC established a protocol guideline for those who should get the vaccine first. By late December to January, a vaccine against H1N1 was available in moderate supply worldwide. The numbers of infected patients began to recede and the pandemic ended. However, a strain of H1N1 was incorporated into the yearly trivalent vaccine for the 2010-2011 flu season because the virus was present in the world populations.
As stated in the first section of this article, a new strain of swine flu, (H3N2)v, was detected in 2011; it has not affected any large numbers of people in the current flu season. However, another antigenically distinct virus with the same H and N components (termed H3N2 (note no "v") has caused flu in humans; viral antigens were incorporated into the 2013-2014 seasonal flu shots and nasal spray vaccines.
In India in 2015-2016, a large outbreak of swine flu has been ongoing; there are some researchers who claim the strain of virus has mutated slightly and has become able to cause more severe infections.