Only a few people here are sick. Hardly anyone is panicked, yet. But across the large Asian American communities of Southern California, the global outbreak of a dangerous lung disease so new and mysterious that most residents hardly know its name has begun stoking widespread fear and causing growing disruptions.

The phones are hardly ringing at Dragon Travel Service in Chinatown. Owner Stephen Tong says the illness known as severe acute respiratory syndrome, or SARS, is wiping out his business. Before the disease was discovered in Hong Kong last month, he had been booking about 14 trips a week to Asia. Now he's lucky if he gets two.

In the nearby suburb of Monterey Park, where a majority of residents are Chinese immigrants, pharmacies are besieged by customers clamoring for surgical masks -- either to wear for daily protection from the disease or to send to worried family members in China. But for most, the search is futile. Stores are sold out. And new shipments will take weeks to arrive.

"More and more people are coming in all the time trying to get them," said Amy Lin, who works at a drugstore. "I see them going to all the pharmacies around here. But no one has any of them left, and we can't get more of them. The orders are all backed up."

At last report, medical authorities had identified 2,270 cases of the fast-spreading respiratory disease worldwide, 79 of which have proved fatal. About 100 suspected cases, nearly all of them people who traveled internationally recently, are being monitored in the United States, but no quarantines have been declared and no deaths have occurred.

The Centers for Disease Control and Prevention said today that California has two dozen cases, more than any other state. Health officials in the state are investigating seven other potential cases. In the greater Los Angeles area, which is home to more than a million residents of Asian origin and hundreds of businesses that have close ties to China, about 10 suspected SARS cases are being closely evaluated.

Here and in the many Asian communities around San Francisco, anxiety over the puzzling disease is soaring: Business groups are postponing trips to China -- or turning away delegations from there that had been planning to visit. Families are canceling vacations. Hospitals and clinics are getting deluged with calls from people who believe they might have symptoms of the illness. Restaurants and shops are reporting declines in business and say that some patrons have confessed that they no longer want to venture into largely Asian areas around Los Angeles because they fear they could catch the illness.

Twice this week, that concern has suddenly spiked. The first instance was when public health officials in San Jose temporarily isolated a jetliner that had arrived from Asia carrying five passengers exhibiting signs of the disease that later proved to be false. Then, the World Health Organization took the unprecedented step of warning travelers to avoid Hong Kong and the Chinese province of Guangdong, the suspecting seeding grounds of the epidemic.

That news has Lucy Kelley, executive director of the Monterey Park Chamber of Commerce, thinking twice about hosting any more business groups that regularly come from China to make deals with local merchants. She said the chamber is reluctant to halt the trips, but may have no choice.

"This is such a dilemma." Kelley said. "We don't want to close the door in their faces, but we feel like we may be putting ourselves at risk. This disease is so mysterious. Maybe we should put an end to all the trips until they find a cure."

At Garfield Medical Center in Monterey Park, people with ordinary fevers and coughs are rushing into emergency rooms because they fear they have contracted SARS, whose symptoms initially resemble the flu. Others feeling ill are calling with urgent questions about the disease, and doctors sometimes cannot give clear answers because so much about how it develops and spreads is unknown.

But no local cases have been identified. "Everyone I talk to is asking me about it," said David Langness, a spokesman for the medical center.

In Chinatown, some merchants said that talk of the disease among customers is becoming hysterical. Kenneth Yee, a pharmacist at a drugstore in the neighborhood, had only a few surgical masks left for sale. "I think they are mostly overreacting," he said. "People ask if we have treatment for it. I tell them there is none at this point."

At Queen's Bakery down the street, Winnie Zhou, a Chinese immigrant busy making pastries, said she had been planning to take her 10-year-old daughter to China for the first time this summer, but now wonders if that is wise.

"I want her first time there to be fun and not have her worry," Zhou said. "Maybe we'll just have to go next year. Maybe things will be better then."

The Los Angeles Chinese Chamber of Commerce became the latest group to delay or cancel an upcoming trip to China and Taiwan that had been arranged by the tour company that Edwin Choy works for in Chinatown. He said a few travelers are switching their destination to Japan, where no cases of SARS have been reported, but most are deciding to stay here, at least for the next months.

"Over the last two weeks, business is down 50 percent," Choy said.

Luont Huymt, a clerk at the Hing Fat Company, a Chinatown grocery and herb store, said his business is declining in part because customers have told him they do not want to risk coming into contact with people who have traveled recently to Hong Kong.

"Nobody's coming in here now," he said. But he understands some of their fears about the disease. He is delaying plans to see relatives in Vietnam because of the epidemic.

"I wouldn't go over there now," he said.

An unidentified man wears a mask for protection from SARS after arriving at Los Angeles International Airport from Beijing yesterday.