* Cat infection shows other species can get swine flu
* Owners urged to take care with sick animals
By Maggie Fox, Health and Science Editor
WASHINGTON, Nov 6 (Reuters) - People who think they may have H1N1 flu need to stay away from work, avoid sneezing on their spouses and children and now, they have someone else to worry about infecting too -- their pets.
U.S. vets reported this week that a pet cat had been infected with the pandemic swine flu virus, apparently by its owners, who had reported flu-like illness in the days before.
Two pet ferrets also caught flu, again apparently from their owners, and several herds of pigs around the world have been reported infected.
Animals have long been known to be a source of new infections. Influenza itself originates in birds, possibly domestic ducks. AIDS appears to have come from chimpanzees and possibly gorillas. Ebola virus comes from bats while rabies is spread by many different species.
And this strain of H1N1 very likely originated in pigs although it is now infecting almost exclusively humans.
But with flu, at least, it can go the other way, too.
"This is just another illustration of why influenza viruses are so tricky and frustrating and interesting at the same time, is this ability to occasionally jump species," said Dr. Carolyn Bridges of the U.S. Centers for Disease Control and Prevention.
Bridges said it is impossible to know how many pets may have been infected -- this particular cat lived near a sophisticated animal laboratory in Iowa where vets ran an influenza test out of curiosity. The good news is that the cat survived.
Even for people, it is difficult to find out if a fever, cough and stuffy nose was the swine flu or something else because ordinary flu tests can miss H1N1 and doctors do not have easy access to the more sophisticated test needed to diagnose it.
So no one knows how often pets might get infected. But if there is a season for it to happen, this would be it, says Bridges.
"We have a great deal more disease now than we have in a typical flu season," she said in a telephone interview.
"With the higher numbers of infected people, that increases the possibility of seeing these transmissions."
Cats were known to get H5N1 avian influenza, which is still circulating and which has killed snow leopards and tigers that were fed infected chickens. A strain called H3N8 can sicken and kill pet dogs, Bridges added.
"It is hypothesized that dogs got it from horses. There is potential, certainly, for cross-species infection," she said.
This is bad news for sick pet lovers.
"Even though I think when I am sick in bed the best thing I can have is my cats piling in with me, we realize that is no longer a risk-free activity," said Dr. Julie Levy of the University of Florida, a specialist in pet diseases.
"When a pet is sick we should use common sense -- wash hands, not let them kiss us in the face," Levy added.
According to the World Health Organization, H1N1 has killed at least 6,071 people worldwide and likely far more.
The Sweden-based European Centre for Disease Prevention and Control projects the virus could kill up to 40,000 people across Europe and be followed by seasonal flu waves that could kill the same number.
The international veterinary disease agency, the OIE, says it is compiling reports of H1N1 in animals.
"It is very likely that there will be additional findings of other influenza strains," OIE Director Dr. Bernard Vallat said in a statement.
(Editing by Sandra Maler)