The toll from a new life-threatening respiratory illness mounted yesterday as the number of suspected cases worldwide surpassed 2,600 and the number of deaths reached at least 100.

The World Health Organization reported the number of cases of severe acute respiratory syndrome, or SARS, under investigation hit 2,601 in 17 countries, an increase of 85 cases since Saturday. The WHO reported 98 deaths, with two new deaths in Canada, four in mainland China and three in Hong Kong. In addition, Singapore reported two more deaths.

The number of suspected U.S. cases climbed to 148 in 30 states, including two in Virginia, according to the federal Centers for Disease Control and Prevention in Atlanta. All but a handful have been among people who recently traveled in Asia. No deaths have been reported in the United States.

As the numbers continued their steady rise, health officials in the United States and elsewhere expressed uncertainty about whether the epidemic was coming under control or would continue to spread.

"What we have here is an epidemic . . . that is causing problems in every corner of the globe," CDC Director Julie Gerberding told senators at the first congressional hearing on the new disease. "We don't know where this is going. We have to be prepared for this to continue to spread."

Gerberding appeared yesterday with Anthony S. Fauci, director of the National Institute of Allergy and Infectious Diseases, as well as David L. Heymann, director of WHO's communicable disease program, who participated via satellite.

"We have to be ready for the worst," Heymann said.

In addition to the cases reported by WHO, officials in India reported what could be the first case of SARS in that densely populated nation -- a U.S. citizen who fell ill after arriving in Bombay from China.

In China, the government reported an updated total of 1,268 cases and 53 deaths. The majority of cases have been in Guangdong province, where the epidemic is believed to have begun in November. A WHO team is continuing to gather information about the beginnings of the epidemic there in the hopes of getting a better idea of what to expect in the rest of the world.

Hong Kong continued to report the largest number of new cases -- 83 -- pushing the total there to 883, with 23 deaths. The epidemic has put severe strains on the city's hospitals because many of the cases have been among hospital workers themselves.

A troubling outbreak involving 268 cases at Hong Kong's Amoy Gardens apartment complex, however, appeared to be "coming to an end," WHO said. Investigators have found evidence that the disease may have spread in the apartment building through feces, "though no conclusions have been reached," the agency reported.

In Singapore, which has also been hit hard, officials were investigating what WHO called an "unusual cluster" of 29 suspected cases among hospital workers from two wards of a single hospital, who all appear to have developed symptoms on March 29. "It would be unusual for so many cases to begin on the same day if caused by contact with a patient," WHO said, raising the possibility the disease was being spread by some kind of environmental contamination.

Outside of Asia, Canada has been hit hardest by SARS. The number of Canadians suspected of having been stricken by the disease has reached 226, including 10 deaths, with 188 of the cases occurring in the Toronto area.

SARS is believed to be caused by a microbe known as a coronavirus. Such viruses usually cause nothing more serious in humans than the common cold. There is no vaccine, and no drugs appear effective.

Julie Gerberding, Centers for Disease Control and Prevention director, discusses SARS at a Senate hearing yesterday.