others are buying vitamins to strengthen their children's immune systems, Americans with no plans to travel to Asia are snapping up respiratory masks, and a Wall Street economist has predicted a global recession, all linked to fears about the new respiratory disease, severe acute respiratory syndrome, or SARS.

In the absence of conclusive scientific information about the disease, the public is grappling with it on its own, unapologetically laymen's, terms. Rumors and angst about SARS, fueled by the Internet and a public primed for biological apocalypse, appear to be accelerating faster than in previous disease outbreaks and spreading more widely than the disease itself.

"I think that SARS could be a potential pandemic," said Monty Tabor of Halifax, Nova Scotia, who started an e-mail discussion group with the admittedly alarmist title "SARS: the new plague."

The illness tops the "buzz index" on Yahoo, the popular Internet search engine, and rose to second place last week — after Al Jazeera — from No. 8 on the search engine Google's "zeitgeist" list. Countless Web sites are posting news stories, personal accounts and speculation about the disease.

The variety of responses may reflect an abiding fear of infectious diseases rooted in a time before inoculation vanquished arch-villains like polio and smallpox, medical historians said.

The responses may also simply represent any given individual's best effort to deal with a new unknown — even one that has not resulted in any deaths in the United States.

"Whenever there is ambiguity, people will search for more certainty," said Kathleen Tierney, director of the Disaster Research Center at the University of Delaware. "When people go to the Web they often get conflicting information, which generates more searching and just intensifies the process."

Public anxiety over a novel disease is a familiar pattern tracing from the Black Plague through the West Nile virus, public health officials said. Experts said much of the response, including people canceling trips to Asia, is perfectly reasonable given how little is known about the syndrome.

Other responses are less rational. The Web site Spiritoftruth.org.nz calculates that the entire United States population will be infected in about 23 weeks if new cases continue to double every week (defying the nature of how infectious diseases spread). An Internet site devoted to collecting urban legends and rumors, Snopes.com, has been fielding a barrage of e-mail messages about the illness, many of them anti-Chinese (that the disease originated with people in Hong Kong eating dogs that had it, that workers at Chinese restaurants have the disease, and so on).

A favorite Internet rumor, that the disease is the result of a genetic engineering experiment run amok, fits the template of similar rumors that circulated about AIDS and hantavirus. Perhaps easily dismissed as a standard conspiracy theory, it may speak to a desire to predict and manipulate the world that biological reality does not always provide.

"For a lot of people, it's more comfortable to believe that the C.I.A. cooked something up in a secret lab somewhere and it got out than to realize that new diseases come into being all the time," said Barbara Mikkelson, who runs Snopes.com. "You can just fire the C.I.A., or get a better government. What are you going to do about nature?"

As anxiety — or at least fixation — on the illness intensifies, public health officials are seeking to calm fears and avoid the kind of panic behavior that occurred in October 2001, when several letters containing anthrax were sent through the mail. Some people ended up microwaving their mail and sought to corner the supplies of the antibiotic Cipro at their local pharmacies.

"You don't want people to hurt themselves in some other way in an effort to avoid an infection like this," said Vicki Freimuth, associate director for communications at the Centers for Disease Control and Prevention. "It's critical that a credible source out there is giving information about what we know so people don't turn to other sources that might be more alarmist."

The C.D.C.'s efforts include significantly stepped-up communication with news organizations, which it hopes in turn will convey accurate information to the public. As of April 1, the agency had held 1,300 interviews and eight news conferences, set up for television outlets, which had complained during the anthrax scare when the telephone conference calls were the chosen communications mechanism.

Worldwide, health officials have reported more than 2,000 cases and more than 80 deaths. But of the 100 suspected cases in the United States, no one has died, and C.D.C. officials emphasize that most Americans do not have to worry about catching the disease.

Such increased public outreach does not appear to have quelled the furor: the agency's hot line is now fielding more than 1,000 calls a day, double the number of just a few days ago and more than at any time during the anthrax attacks.

Kimberly Wood, 40, of Hazleton, Pa., says that she has been absorbing all the information she can about SARS, but that nothing has addressed her concerns. She has been feeding her children extra vitamin C and has stocked up on powdered milk and canned vegetables in case the disease comes to the East Coast.

"I almost laughed at the people who were so worried about West Nile," Ms. Wood said. "I don't worry about anything like this, but for some reason SARS really got me. So I'm preparing, just in case."

Personal precautions vary by profession, geographical location and risk profile.

A dental hygienist at an office on the Upper West Side of Manhattan is asking her patients if they have traveled recently to Asia. If so, she asks them to put off their appointments for a month.

The American Association for Cancer Research canceled its annual meeting in Toronto, where several of the cases have been diagnosed. The flight attendants union has demanded that airlines supply protective gloves and masks to employees on flights to Asia. The island country of Mauritius, in the Indian Ocean, has suspended its two weekly flights to Hong Kong for a month.

Jack Androski, a sales analyst in Manhattan, settled for trucking in antioxidants after returning from a vacation last week to find his roommate, a personal trainer, had come down with a cough. "We had a long conversation about it over the breakfast table," said Mr. Androski, 30. "We were like, `Is this SARS?' But so far I haven't gotten it."

What drives some of the less-than-rational fears over the illness, medical experts say, are both a lack of understanding among the public of how infectious diseases are spread, and an enduring human suspicion, no matter how much we may understand intellectually, of things we cannot see.

"There's something about germs and bugs being transmitted invisibly that is a very powerful scary image for people," said Baron Lerner, a historian of medicine and internist at Columbia University. "These diseases that pose less of a threat to people than many things they do in their daily lives, like riding a car, nevertheless cause anxiety above and beyond what is warranted."

Most people may know that the number of deaths due to infectious illness has dropped sharply, from over 90 percent before World War II to about 5 percent today. But for reasons that are themselves also largely irrational, risks that are new and exotic also tend to draw more fevered concern than those that are more dangerous.

"When a new strain of influenza, which kills on average 30,000 people a year in the United States, appears, we don't see this kind of attention paid to it," said Henry Miller, a fellow at the Hoover Institution at Stanford University. "It's the psychology of risk perception. People have far less concern about risks that they think they understand."

Ronald Arakelian, a doctor of internal medicine in Turlock, Calif., thinks his risk perception is just fine — and he has been calling every health official in the state to voice his concern about SARS.

"I'm sitting out here in California, which is the epicenter of where this could break out," Dr. Arakelian said. "The thing I'm trying to understand is, is the government for whatever reasons, political or economic, going to allow this deadly virus, and that's not an exaggeration, to spread throughout this country? I'm not on the lunatic fringe, but am I panicky? I'm probably the most panicky person here."