The origin of the virus that killed 774 people remains unknown. Scientists believe people may have gotten the virus from animals that were infected by another source.
"You might want to quarantine the pets as well as the people," suggested Dr. Robert Shope, an expert on emerging diseases at the University of Texas Medical Branch in Galveston. "If it's been shown that the virus can transmit from cat to cat, it doesn't take much of a leap of faith that it will transmit to humans."
Other scientists who have studied SARS say pet owners shouldn't overreact, however.
"These animals in all likelihood did not play a significant role in spread of (SARS) to humans," said Dr. Klaus Stohr, the World Health Organization's chief SARS scientist.
Researchers discovered the vulnerability of cats and ferrets to SARS while searching for animals to test potential vaccines.Their study, also notes a separate report that cats were found infected with the virus in a Hong Kong apartment complex where residents contracted SARS last year.
Cats and ferrets are the first pets included on an exotic list of animals scientists think may be able to harbor the virus. However, the virus seems to be so versatile that it could have jumped to humans from a variety of animals, co-author Albert D.M.E. Osterhaus said.
In China, where SARS festered for months before it grew into a worldwide menace this year, exotic raccoon-dogs, ferret badgers and civets imported into markets have been found harboring a germ that's almost identical to the SARS virus.
Because of the possibility that animals can spread the respiratory virus, WHO has suggested that animals in China and elsewhere be tested for SARS and other diseases before they are eaten.
For the Nature study, researchers inoculated six cats and six ferrets with the virus cultured from a person who died of SARS, adding drops that contained the virus into their trachea, eyes and nose.
The cats and ferrets began to show their infection two days later in excretions from the throat, and researchers found they produced antibodies within 28 days. When the animals were later euthanized, the virus also was found in their respiratory tract.
The cats did not appear to be affected by the virus, but they did develop a mild case of pneumonia. The ferrets became lethargic, and one of them died four days after it was inoculated.
Scientists also placed two healthy cats and two healthy ferrets with the infected animals. The healthy ferrets showed signs of SARS infection after two days. The ferrets became emaciated and eventually died about two weeks later, but researchers said they were uncertain whether this was due to the virus.
Researchers said the healthy animals were infected so quickly that they wondered whether the cultured virus was simply rubbed onto them from close contact with their recently inoculated cage mates.
However researchers said too few animals were used to reach a firm conclusion about how cats and ferrets become infected.