[cnn-photo-caption image=http://i2.cdn.turner.com/cnn/2009/HEALTH/04/24/swine.flu/art.pigs.gi.jpg caption="Swine flu is usually diagnosed only in pigs or people in regular contact with them."]
U.S. Centers for Disease Control and Prevention
What is swine influenza?
Swine influenza (swine flu) is caused by type A influenza virus and gives pigs the flu. Swine flu viruses cause regular outbreaks of flu in pigs but death is infrequent. The viruses may circulate among pigs throughout the year, but most outbreaks occur during the late fall and winter months similar to outbreaks in humans. The classical swine flu virus (an influenza type A H1N1 virus) was first isolated from a pig in 1930.
How many swine flu viruses are there?
Like all flu viruses, swine flu viruses change constantly. Pigs can be infected by avian, human and swine influenza viruses. When influenza viruses from different species infect pigs, the viruses can reassort and new ones emerge that are a mix of swine, human and/or avian influenza viruses. Over the years, different variations of swine flu viruses have emerged. Right now, there are four main influenza type A virus subtypes that have been isolated in pigs: H1N1, H1N2, H3N2, and H3N1. However, most of the recently isolated influenza viruses from pigs have been H1N1 viruses.
Can humans catch swine flu?
Swine flu viruses do not normally infect humans. However, sporadic human infections with swine flu have occurred. Most commonly, these cases occur in persons with direct exposure to pigs, such as children near pigs at a fair or workers in the swine industry.
There have been documented cases of one person spreading swine flu to others. In 1988, an outbreak of apparent swine flu infection in pigs in Wisconsin resulted in multiple human infections, and although no community outbreak resulted, there was antibody evidence of virus transmission from the patient to health care workers who had close contact with the patient.
How common is swine flu infection in humans?
In the past, the U.S. Centers for Disease Control and Prevention received reports of about one human swine flu virus infection every one to two years in the U.S., but from December 2005 through February 2009, 12 cases of human infection with swine flu have been reported. Five of the 12 cases occurred in patients who had direct exposure to pigs, six in patients reported being near pigs, and the exposure in one case was unknown.
What are the symptoms of swine flu in humans?
The symptoms of swine flu in people are expected to be similar to the symptoms of regular human seasonal influenza and include fever, lethargy, lack of appetite and coughing. Some people with swine flu also have reported runny nose, sore throat, nausea, vomiting and diarrhea.
Can people catch swine flu from eating pork?
No. Swine flu viruses are not transmitted by food. You cannot get swine flu from eating pork or pork products.
How does swine flu spread?
Influenza viruses can be directly transmitted from pigs to people and from people to pigs. Human infection with swine flu viruses are most likely to occur when people are in close proximity to infected pigs, such as in pig barns and livestock exhibits at fairs.
Human-to-human transmission of swine flu can also occur. This is thought to occur in the same way as seasonal flu occurs in people, which is mainly person-to-person transmission through coughing or sneezing of people infected with the flu virus. People may become infected by touching something with flu viruses on it and then touching their mouth or nose.
What is known about human-to-human spread of swine flu?
In September 1988, a healthy 32-year-old pregnant woman was hospitalized for pneumonia and died eight days later. A swine H1N1 flu virus was detected. Four days before getting sick, she had visited a county fair swine exhibition where there was widespread flu-like illness among the pigs.
In follow-up studies, 76 per cent of swine exhibitors tested had antibody evidence of swine flu infection but no serious illnesses were detected among this group. Additional studies suggest that one to three health care personnel who had contact with the patient developed mild influenza-like illnesses with antibody evidence of swine flu infection.
How are human infections with swine flu diagnosed?
To diagnose swine influenza A infection, a respiratory specimen is ideally collected within the first four to five days of illness and sent to the CDC for testing.
What medications are available to treat humans with swine flu?
Four antiviral drugs are licensed for use in the United States: amantadine, rimantadine, oseltamivir and zanamivir. While most swine flu viruses have been susceptible to all four drugs, the most recent seven swine flu viruses isolated from humans are resistant to amantadine and rimantadine. Right now, the CDC recommends oseltamivir or zanamivir for the treatment and/or prevention of infection with swine flu viruses.
What other examples of swine flu outbreaks are there?
The most well known outbreak of swine flu was 1976 one among soldiers in Fort Dix, N.J. The virus caused illnesses in at least four soldiers and one death; all were previously healthy. The virus was transmitted in close contact at a basic training camp. It was thought to have circulated for a month and disappeared. The source of the virus, the exact time of its introduction into Fort Dix and factors limiting its spread and duration are unknown. The outbreak may have been caused by introduction of an animal virus into a stressed human population in close contact during the winter.
Find More on Swine Flu from the U.S. Centers for Disease Control and Prevention
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