TORONTO - The number of people with SARS in Canada's largest city tripled to 33 yesterday when health officials broadened their definition of what constitutes a "probable case" to meet international standards.
The change came after the World Health Organization on Wednesday urged Canada to expand its definition of severe acute respiratory syndrome.
The new cluster of cases in Canada, first detected last week, was a harsh blow to a health care system that appeared to have brought an initial SARS outbreak in March and April under control.
Health officials have told more than 7,000 people to quarantine themselves because of possible exposure.
Elsewhere yesterday, Taiwan reported 50 new cases of severe acute respiratory syndrome, its biggest rise in six days. Officials insisted that Taiwan's outbreak was declining, and said yesterday's jump included 40 patients who had earlier tested negative and were later reclassified as confirmed.
China reported just three new cases, the lowest daily number so far.
The global death toll from SARS was at least 753, out of more than 8,200 people infected since November, mostly in China and Hong Kong.
Because of the new cluster in Canada, Toronto was placed again on the World Health Organization's list of SARS-affected areas.
Another 29 cases were listed as suspected, and officials warned that 107 other people showing possible SARS symptoms were being monitored.
"I think a large number of them will eventually be suspect or probable cases," said Dr. Donald Low, chief microbiologist at Mount Sinai Hospital and a key figure in Toronto's anti-SARS efforts.
Officials worry that the World Health Organization could issue another warning against travel to the city, like one on April 23 that was lifted a week later.
WHO spokesman Iain Simpson said yesterday that the United Nations agency was not considering another travel advisory.
"It's a subjective judgment," Simpson said. "We look at whether there is a high level of risk and if there are things we don't understand before we take any decision."
He added that the agency was "watching the situation closely and monitoring it closely."
A total of 29 people have died in the Toronto area since the illness first appeared from Asia in early March in the biggest outbreak outside of Asia. Four probable cases remained hospitalized yesterday.
The new SARS cases mean further harm to Toronto's crucial convention and tourism industry. Officials have started aggressive marketing campaigns to lure back visitors after the initial SARS outbreak, including packages of cheap prices for lodging, meal and tickets to theater, ball games and other entertainment.
Organizers announced yesterday that all 70,000 tickets for a June 21 concert to promote Toronto tourism had sold out in three hours. Performers will include Avril Lavigne, the Barenaked Ladies and Sarah McLachlan.
Prime Minister Jean Chretien promised that his government would provide financial help to fight SARS in Toronto, and insisted that the city is safe to visit.
In response to the new cases, health authorities reimposed strict controls on Toronto-area hospitals - closing those where the new cases were found to new patients and limiting access to emergency rooms in all others.
Despite the SARS scare, life has continued as usual in the metropolitan area of more than 3 million people on the north shore of Lake Ontario.
Almost no one wears masks in the bustling downtown streets, and restaurants, theaters and other entertainment venues remain open despite complaints of decreased business because of SARS.
Health officials said the increased figure for new probable SARS cases was expected because of the altered definition.
"They're getting higher, but they're not higher per day at this period of time," said Dr. James Young, the Ontario commissioner of public safety.
"We're not seeing large numbers of cases coming into the system each day."
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