A 26-year-old Hong Kong woman who traveled to the United States last week is under watch at a Baltimore hospital as the state's first potential SARS patient, and nine of her family members have been isolated in a Bolton Hill apartment building.

The woman's symptoms do not fully match the definition of a SARS case, and the only relative who had any signs of illness - a 17-year-old cousin, also from Hong Kong - was released from Maryland General Hospital yesterday after doctors determined he did not have the disease.

Still, city and state health officials said they decided to take an overly cautious approach and ask that all of the woman's relatives remain isolated for three days while physicians monitor her symptoms.

"We don't know that this woman has been exposed to SARS in Hong Kong, but we're treating her like she may have been," said Dr. David Blythe, epidemiologist for the state Department of Health and Mental Hygiene. "I think we want to all be very cautious about this."

He said that blood, stool and respiratory specimens are being sent to the Centers for Disease Control and Prevention in Atlanta for evaluation to determine whether a coronavirus is present. A new member of that virus family has been identified as the cause of the worldwide SARS outbreak.

The CDC has reported 190 suspect cases and 38 probable cases of severe acute respiratory syndrome in the United States. None have been fatal.

Health officials said yesterday that the woman, who is in good condition, went to the emergency room Monday with the 17-year-old boy after another family member - who is a medical resident at the hospital - became concerned about their symptoms.

Dr. Chandralekha Banerjee, director of infection control at Maryland General, said that because the family member called ahead, health care workers were able to prepare themselves with protective gear, including face masks, goggles, gowns and gloves.

Masks were placed on the two patients before they entered the building, and both were immediately put in a room with negative air pressure to keep contaminants from circulating throughout the hospital.

The woman was admitted to the hospital Monday evening. Though an initial chest X-ray raised concern about the possibility of pneumonia, which occurs in many serious SARS cases, further testing yesterday ruled that out, health officials said.

The teen-ager, whose chest X-ray was normal, was held overnight Monday in the emergency department for observation but was released yesterday. He is now in isolation with the woman's other relatives at a one-bedroom apartment in Sutton Place, where the medical resident lives. None of the others have shown SARS-like symptoms.

The isolation measures are beyond what the CDC recommends for people who may have come into contact with a SARS patient, but city and state health officials said they wanted to be proactive.

"We just are trying to be prudent and cautious," said Blythe, the state epidemiologist.

Dr. Peter L. Beilenson, Baltimore's health commissioner, said that the woman, a secretary at a watch-making shop in Hong Kong, flew from that city to New York on April 15 for an engagement party in Queens. She developed SARS-like symptoms, including a fever and a cough, the next day, he said.

She and several other relatives decided to visit Baltimore and took a bus that arrived downtown about 2 a.m. Sunday, Beilenson said. Health officials are trying to track other passengers on the bus to make sure they haven't developed symptoms, but are unaware of anyone else becoming sick. It is not clear whether all of the family members in isolation - who range in age from 6 to 30 and are from several different countries - came from New York by bus or some other means.

When the woman's cough didn't clear up, the medical resident became concerned and called Maryland General.

Several health officials said yesterday that the woman and the teen-ager would likely have been given antibiotics at the hospital and sent home if they had not recently been in Hong Kong. That region has reported more than 1,400 cases of SARS and 99 deaths.

"The key thing for both of them - the real red flag for both of them - was that they were from Hong Kong," said Lee Kennedy, a Maryland General spokesman. "That seemed to be what piqued our interest as well as the resident who called the ER to say, 'I'm bringing in my relatives to be seen.' "

Beilenson said last night that the woman's fever had fallen from 100.1 degrees to about 99.9. SARS is generally characterized by a fever of 100.4 or more.

Though this could be Maryland's first case of SARS, the health commissioner stressed that the public should not panic.

"In the strongest possible terms, absolutely, positively, the general public does not have to worry about this and should not go out and get masks and be concerned about this," Beilenson said. "We are simply being proactive and letting the public know that there is a potential case. We are actually going well beyond CDC guidelines in an attempt to ensure, even if this was a case, it doesn't spread out this one individual."

As they returned home last night, Sutton Place residents didn't seem overly concerned. Many said they appreciated the city health department's quick response in leaving information leaflets under their doors and having health officials - including Beilenson - available in the high-rise building's lobby to address their questions.

"Some people are going to panic, but that comes with anything like this," said Ryan Carey, 22, who has lived in the building for nearly a year. "I'm really not concerned. I'm aware that it's a close-contact kind of a disease and people in the building pretty much keep to themselves."

Charlene Perry, 36, a resident since August, was more philosophical. "If it's your time, then it's your time. I get exposed to stuff everyday," said Perry, a physician's assistant. "It's too early to panic."

Sun staff writer Johnathon E. Briggs contributed to this article.