Overheated with fever and a case of anthrax jitters, Monica Reeves took a break from her hour-long wait in an emergency room to fan her face with some fresh air.

Nine days ago, she stood in line more than an hour to mail certified letters at a post office later found to be contaminated with anthrax. Since then, she's felt like she has the flu.

"My fever is 100.4 degrees today," Reeves, 26, of Upper Marlboro, Md., reported Wednesday as she stood in the ambulance bay at George Washington University Medical Center. "My chest is really sore and I have the sweats. I never sweat and I've been sweating for the past three days."

Is it the flu or anthrax?

Since both illnesses start with similar symptoms -- fever, cough, headache, vomiting, chills, weakness, abdominal pain -- medical officials around the nation are gearing up for a confusing influenza season.

Reeves' doctor wasn't sure whether she had contracted inhalation anthrax at the Brentwood post office in Washington, so he prescribed antibiotics and sent Reeves, a computer analyst at the World Bank, to the hospital to be tested. She'll get the results in a few days.

Family doctors in the few cities where anthrax has been discovered are getting the brunt of calls from skittish patients, yet physicians across the nation are learning about the disease too.

Medical workers are tuning in to Webcasts produced by the federal Centers for Disease Control and Prevention and other organizations. They're calling information hotlines and reading guides on how to distinguish the disease from influenza, which typically peaks between January and March and kills as many as 20,000 Americans each year.

"The level of concern and suspicion is relatively high in the medical community," said Dr. Timothy Flaherty, chairman of the American Medical Association and a diagnostic radiologist in Wisconsin. "But it depends on what area of the country you are in."

Flaherty said the critical question for doctors is whether a patient has been exposed to anthrax. Other questions that need asking, he said, are: Has the patient been around other people who have the flu? Have they been anywhere where they could have been exposed to anthrax? Did they get a flu shot this year?

As it does every year, the AMA is recommending flu shots, which could help doctors rule out the virus as the cause of flu-like symptoms. Conversely, flu test kits, now available in some doctor's offices, can be used to quickly confirm a flu diagnosis and alleviate any fears of anthrax.

"All of us are pushing the flu shots so we can cut down on symptoms that look like anthrax," said Dr. Barry Prystowsky, a pediatrician in Nutley, N.J., who is sticking all his patients with needles full of flu vaccine.

A complicating factor is that deliveries of flu vaccine are running late again this year, and health officials are urging anyone but high-risk patients -- typically the very young and the very old -- to wait until November or December to get their shots.

Nutley is north of Trenton, N.J., the postmark of at least three anthrax-laced envelopes, sent to Senate Majority Leader Tom Daschle, NBC anchorman Tom Brokaw and The New York Post. Prystowsky said he and his colleagues have been instructed to call a state-run hotline if they treat someone with flu symptoms who had been in an area contaminated with anthrax.

In Washington, Dr. Byron Cooper's office is being besieged by calls.

"The question is: `I received mail from D.C. I want to be screened,"' said Cooper, a pulmonary internist who is not recommending anthrax tests for people who have not been exposed. "I had so many of those types of calls that I got like an hour behind."

He expects more calls as winter approaches and people get colds and fevers.

"The flu is going to be a confusing matter," Cooper said. "So far, my patients are calling without symptoms, except one who had a scab inside her nose and wondered whether that was from inhalation anthrax.

"Anyone who calls with flu symptoms, I'm going to tell them they need to come in and be evaluated. I'm sure we'll be deluged."

In Brunswick, Maine, Dr. Meryl Nass is getting few calls from her patients even though she's an expert on anthrax who has studied cases of the disease around the world. "I think that people are settled down a bit knowing that there are antibiotics out there," Nass said.

There's no way to distinguish between anthrax and the flu without doing specialized tests, but there are some clues, said Nass, who is helping design a practice case to help doctors diagnose anthrax. She read from a list of symptoms in a hypothetical case: "Nasal congestion, sore throat, low grade fever and a cough that is occasionally productive of sputum."

This patient probably did not have anthrax, she said.

"Anthrax doesn't cause sputum," she said. "Although people may be short of breath and they might have a dry cough, they are not producing anything in the lungs."

Except for slight soreness in his throat, Wesley Barriteau, 41, of Laurel, Md., doesn't have any flu-type symptoms. Still, since he works with mail sorting equipment and had been in two buildings that handle mail for Congress, his employer, Bell and Howell, sent him to the hospital emergency room for testing.

"I'm fine," he said, patting his throat with the back of his hand as if checking himself for fever.