Atlanta ? Federal officials said Thursday the new respiratory virus that began in Asia may have spread for the first time in a workplace in the United States.

Dr. Julie Gerberding, head of the Centers for Disease Control and Prevention, said a suspected SARS virus patient who became ill after traveling to Asia may have infected a co-worker in Florida.

Gerberding said she was “very concerned” about the possible spread of the disease and the Florida case is being investigated.

The case is in the Gainesville area. A 47-year-old woman is believed to have been infected at work by a 60-year-old woman who was the county’s first suspected SARS case, said Tom Belcuore, director of the Alachua County Health Department. The older woman had recently traveled to Asia.

Until now, severe acute respiratory syndrome has appeared to spread only to family members or health workers who have had close contact with an infected person.

So far, a dozen people — nine family members and three health workers — had been infected in that manner. The rest of the 166 suspected cases in this country involve people who were infected while traveling in Asia.

In Florida, the workplace spread was found during the Health Department’s routine investigation of one worker’s contacts. The health investigators discovered a co-worker who had a respiratory illness and placed that person on the list of suspected SARS cases.

“It is far too early to know if any of these workers have SARS,” Gerberding said.

But just in case, she said, the CDC will post new guidance regarding SARS patients for schools and the workplace.

“We are asking people to contact their clinician if they have any kind of unusual illness,” she said.

Since the World Health Organization announced a worldwide alert last month about the emergence of SARS, the United States has implemented infection control policies in hospitals and among households of suspected cases.

A SARS case outside close contacts could cause health officials to consider stronger measures for controlling the disease, but Gerberding said the Florida transmission hadn’t been proven yet.

“When we see an unexplained case pop up in a school or workplace, that’s when we are concerned the public health containment efforts have failed,” she said. “But we’re not seeing that at this time.”

Florida officials said a school in Okaloosa County went through an emergency cleaning after a 6-year-old boy suspected of having SARS appeared at school with mild symptoms. Health officials are aggressively monitoring the boys’ contacts at school to make sure no one else is infected, said Rob Hayes, Health Department spokesman. The boy may have been infected from a family member, Hayes said.

“We immediately became aware of it and had the child sent home,” Hayes said. “He’s staying at home with his family until 10 days after symptoms subside.”

Also on Thursday, two teams of doctors reported in a medical journal finding a newly discovered version of the coronavirus, a bug that ordinarily causes common colds, in a total of 27 people believed to have SARS. The work supports the scientific case that this virus causes the disease.

They speculated that the virus might have come from animals, which have their own forms of coronavirus, and mutated in some way so it infects people. However, the scientists have not ruled out the possibility that some other microbe might also be involved, perhaps making SARS more severe or easier to catch.