Studies in guinea pigs have shown that flu is easier to transmit in cold, dry conditions.
In 1988, in an apparent swine flu infection in pigs in Wisconsin, there was antibody evidence of virus transmission from the patient to health care workers who had contact with the patient, the CDC said.
Egypt has ordered the nation's quarter of a million pigs to be slaughtered over swine flu fears, in the first such move in the world, even though experts say the virus cannot be transmitted by eating meat.
According to the CDC, H3N2 flu viruses are common among pigs.
The H1N1 strain of swine flu is usually associated with pigs.
CNN: U.S. prepares for possible swine flu epidemic as global cases rise
Swine flu is a respiratory disease of pigs caused by type A influenza, according to the CDC.
Most of the time, people who get sick from swine flu have been in contact with pigs, and the virus doesn't spread from person to person.
All flu viruses jump from birds to pigs to humans.
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Swine flu is a contagious respiratory disease that affects pigs and can jump to humans.
The CDC describes swine flu as a contagious respiratory disease that affects pigs.
CNN: Inaccurate 'swine' flu label hurts industry, pork producers say
Swine influenza, or flu, is a contagious respiratory disease that affects pigs.
The World Health Organization announced Thursday it would stop using the term "swine flu" to avoid confusion over the danger posed by pigs.
CNN: Inaccurate 'swine' flu label hurts industry, pork producers say
The flu has a nasty habit of jumping the species barrier, hopping to humans from both pigs and chickens.
"Swine flu" was "an unfortunate name for everybody involved in swine production, implying that the pigs were the source of this current outbreak, " Gramer said.
CNN: Inaccurate 'swine' flu label hurts industry, pork producers say
Swine flu is caused by a virus similar to the regular flu virus that circulates in people every year, but is a strain that is typically found only in pigs or in people who have direct contact with pigs.
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