CHICAGO (AP) _ Picture a college student from Vietnam returning to school after a spring break: She's sick, coughing, feverish and seeking treatment at a campus emergency room.

It's a scenario some experts envision as a likely way bird flu could first show up in the United States, and it would immediately set into motion a set of steps hospitals nationwide are nervously planning.

With rising numbers of birds and humans abroad infected with a deadly form of the H5N1 virus, U.S. hospitals need to get ready now, a federal bird flu expert said Tuesday at a meeting of epidemiologists in Chicago.

``It's extremely important to investigate every H5N1 case,'' said Dr. Timothy Uyeki of the federal Centers for Disease Control and Prevention.

A single U.S. human case might be just the start, and scientists need to know if the virus has mutated to become easily spread between humans _ a development that could trigger a global pandemic, Uyeki said.

Health officials don't know if the deadly virus that has decimated Asian poultry flocks will cause a pandemic, but they are fearful because of its rapid and unprecedented spread among fowl, Uyeki said. There are 184 confirmed human cases and 103 deaths linked to the virus. No U.S. cases have been reported.

Many U.S. hospitals are still in the planning stage for a pandemic. But the University of Chicago Hospitals are a bit further along. Patients who arrive there with flu symptoms are routinely asked about recent travel to places where bird flu is rampant.

If a patient said yes and also had contact with live poultry, bird flu would be strongly suspected and the patient would be sent to an isolation room where air flow can't circulate to the rest of the hospital, said Dr. Stephen Weber, a hospital epidemiologist whose job is to control infection outbreaks.

``This is a trigger for what's called the bio-outbreak response plan,'' Weber said, and hospital workers would contact his office. There, the person on call ``would immediately drop what they're doing'' and rush to the treatment area.

Local public health officials would be notified, and the patients' mucous or saliva would be whisked to a tightly controlled state lab in Chicago for tests and diagnosis.

``The last thing you want to do is send a sample to the hospital lab, and grow it. What happens then is you get a concentration of bird flu virus that could put lab workers at risk,'' Weber said.

While that first patient's needs likely could be met with an isolation room, ventilator, and enough doctors and nurses to administer treatment, all of those likely would be scarce in a pandemic.

``Awful'' decisions will be commonplace if a pandemic hits, like whether a very ill 65-year-old patient should be denied a ventilator so that a 25-year-old more likely to survive can get one, said Dr. Andrew Pavia, an infectious disease specialist from Salt Lake City who attended the meeting.

The worst-case scenarios involving an onslaught of hundreds of severely ill patients would force hospitals to shut down some routine services and ration things like hospital beds and antiviral drugs.

Even slightly better scenarios will still stretch hospital resources thin, said Dr. Trish Perl, president of the epidemiology society.

``You have to figure out how you're going to keep a hospital open, delivering babies, and advocate for the patients and advocate for the health care worker and not have it all fall apart,'' said Perl, staff epidemiologist at Johns Hopkins Hospital. ``It's very challenging.''

One way to lessen a pandemic's pain is to increase dismal flu vaccination rates among hospital workers, said Mayo Clinic vaccine specialist Dr. Gregory Poland.

Efforts are under way to develop an H5N1 vaccine. Poland called flu shots ``a moral and ethical duty'' for health care workers.