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.
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.
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.
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