Adapted from information provided by the U.S. Centers for Disease Control (CDC).
Can pigs get the flu?
Interestingly, members of the swine family can and do get the flu! The pig industry routinely deals with flu caused by a type A H1N1 influenza virus. It is called swine flu – but it's not the same virus as the "novel H1N1" or “swine” flu in people. (See “Is the flu that North American pigs get different from human H1N1 flu?” below.)
Like humans, pigs have a flu season, with most outbreaks of swine flu occurring in the late fall and winter months. Many pigs get sick, but most recover.
Pigs can also catch bird flu and human flu. In fact, in 2009 when the so-called swine flu starting affecting humans and caused a pandemic, the National Pork Board was concerned about people who worked in the pig industry passing the novel H1N1 flu to pigs – which did happen at least once. Pigs on a farm in Canada were infected, probably by one of the workers. According to the NPB website at the time, "The virus caused mild illness in the Canadian herd, and the pigs are recovering."
Do these pig flu symptoms sound familiar?
The CDC lists these signs of swine flu in pigs: sudden onset of fever, depression, coughing (barking), discharge from the nose or eyes, sneezing, breathing difficulties, eye redness or inflammation, and going off feed.
Is the flu that North American pigs get different from human H1N1 flu?
“Swine flu” is still the common name for what the CDC calls "novel H1N1" flu, but it’s not the preferred term in scientific circles. The 2009 H1N1 flu was known as swine flu at first because many of the genes in the new virus appeared similar to swine flu viruses normally found in pigs on this continent.
But further study showed that the virus is quite different from the so-called swine flu that typically circulates in North American pigs. Instead, it has genes from flu viruses that circulate in North American and Eurasian pigs, along with genes from birds and from humans. A standard flu shot or nasal spray flu vaccine now provides protection against that particular flu.
Can people catch swine flu from pigs?
Yes, but it’s very unusual. People with direct exposure to pigs – such as children who come into contact with pigs at a county fair, or adults who work in the pig industry – occasionally are infected with the swine flu that North American pigs get. In rare cases such people have spread the illness to others.
(Again, this is not the same "swine flu" that swept across the world in 2009.)
The CDC typically records one human swine influenza virus infection every year or two, although from late 2005 to early 2009, 12 cases were reported.
Then, in 2011, more cases cropped up. Three were in children who had attended Pennsylvania's Washington County Agricultural Fair, one under age 5 and two under age 10. One was known to have had direct contact with a pig, and the other two were in the area in which pigs were being shown.
As of October 2011, there were six cases for the year, bringing to 26 the total number of confirmed cases since 2005.
For those few people who catch flu from pigs, the symptoms are similar to those associated with other types of flu. Flu shots don't provide protection because the viruses are so different from human viruses, but the antiviral drugs oseltamivir and zanamivir may be effective.
Can people catch the flu from eating pork?
No. Flu viruses are spread by close contact between pigs and people, people and pigs, and people and people. You won't catch any type of flu from eating pork.
Raw meat of all types may contain bacteria and viruses, but they're killed by heat in the cooking process.
What's the connection between human flu and animal flu viruses?
Influenza viruses change or mutate constantly. That’s one reason scientists have to devise a new vaccine every year for the annual seasonal flu that hits human populations starting around October. The ever-changing flu viruses in circulation have to be analyzed and, about nine months before flu season, flu shot developers make their best guess as to which strains will dominate during the coming season.
Swine flu viruses are no different. They change constantly, and pigs can be infected by avian (bird) influenza and human influenza viruses as well as the swine variety. When flu viruses from other species infect pigs, the viruses can swap genes, creating new viruses that are some mix of swine, human, and bird flu.
If you're interested in the science of influenza viruses (in this case, reassortment, the process through which influenza viruses swap genetic information), the CDC has detailed information.