The respiratory virus known as SARS has appeared to spread in the United States only to family members or health workers with close contact to an infected person.
But on Thursday, the head of the Centers for Disease Control and Prevention said there may be a case of severe acute respiratory syndrome in the workplace.
Dr. Julie Gerberding said a suspected SARS virus patient who became ill after traveling to Asia may have infected a co-worker in Florida, a development that makes her "very concerned."
So far, a dozen people -- nine family members and three health workers -- were infected after coming into close contact with a person with SARS. The rest of the 166 suspected American cases involve people who were infected while traveling in Asia.
In the Gainesville, Fla., area, a 47-year-old woman is believed to have been infected at work by a 60-year-old woman who was Alachua County's first suspected SARS case, said Tom Belcuore, director of the county's health department.
Gerberding said the CDC will post new guidance regarding SARS patients for schools and the workplace. The Florida case is being investigated.
"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 contact could cause health officials to consider stronger measures for controlling the disease, but Gerberding said the Florida transmission hasn'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 a cleaning after a 6-year-old boy suspected of having SARS appeared at school with mild symptoms. Health officials are aggressively monitoring the boy's 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.
The researchers 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.