Swine influenza virus is common throughout pig populations worldwide. Transmission of the virus from pigs to humans is not common and does not always lead to human influenza, often resulting only in the production of antibodies in the blood. If transmission does cause human influenza, it is called zoonotic swine flu. People with regular exposure to pigs are at increased risk of swine flu infection. The meat of an infected animal poses no risk of infection when properly cooked.
During the mid-20th century, identification of influenza subtypes became possible, allowing accurate diagnosis of transmission to humans. Since then, only 50 such transmissions have been confirmed. These strains of swine flu rarely pass from human to human. Symptoms of zoonotic swine flu in humans are similar to those of influenza and of influenza-like illness in general, namely chills, fever, sore throat, muscle pains, severe headache, coughing, weakness and general discomfort.
Pandemic H1N1/09 virus.
The Pandemic H1N1/09 virus is a swine origin Influenza A virus subtype H1N1 virus strain responsible for the 2009 flu pandemic.
Electron microscope image of the reassorted H1N1 influenza virus photographed at the CDC Influenza Laboratory. The viruses are 80–120 nanometres in diameter
Contagiousness
The virus is contagious and is believed to spread from human to human in much the same way as seasonal flu. The most common mechanisms by which it spreads are by droplets from coughs and sneezes of infected people, and touching a surface or the hand of a person contaminated with virus, and then touching one's mouth or nose.H1N1/09 is more contagious than seasonal flu[11], and infected people are contagious for longer than had been thought. The US CDC had recommended that people should wait at least a day after their fever subsides (usually 3–4 days after the onset of symptoms) before resuming normal activities, but it has been found that they can continue to shed virus for several days after that.[12]
The contagiousness of the virus may change as it mutates.
Vaccine
Main article: 2009 flu pandemic vaccine
Existing vaccines against seasonal flu provide no protection, but as of September 2009 a vaccine for H1N1/09 is in an advanced stage of development, with delivery expected to start in November 2009, although production may be 3 billion doses per year rather than the earlier estimate of 5 billion.
Initial Phase I human testing began with Novartis' MF59 candidate in July 2009, at which time phase II trials of CSL's candidate CSL425 vaccine were planned to start in August 2009, but had not begun recruiting. Sanofi Pasteur's candidate inactivated H1N1 had several phase II trials planned as of 21 July 2009, but had not begun recruiting. News coverage conflicted with this information, as Australian trials of the CSL candidate were announced as having started on 21 July and the Chinese government announce the start of trials of the Hualan Biological Engineering candidate.
Pandemrix, made by GlaxoSmithKline (GSK), was approved by the European Medicines Agency on 25 September 2009, and Baxter's vaccine has been reported as likely to get approved the following week. The first comparative clinical study of both vaccines started on children in the UK on 25 September.
Arepanrix, an adjuvanted vaccine made by GSK, was authorized by Canada's Minister of Health on 21 October 2009.
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