TORONTO — Health Canada placed new restrictions on the collection of blood Thursday to help preclude the possibility of SARS-tainted donations getting into the blood supply.

Dr. Paul Gully of Health Canada announced the changes at a SARS briefing in Ottawa "although there is currently no evidence of transmission of SARS through blood or blood components." The temporary deferral of donations affects people who travelled within the previous 10 days to an affected area outside Canada - China, Hong Kong, Hanoi, Singapore and Taiwan.

As well, those people who have been a patient in, worked in or visited a facility that is under quarantine for SARS are asked to temporarily defer giving blood.

Those facilities are in the Toronto area, and include Scarborough Grace Hospital, where some of the first Canadian SARS cases were treated, and York Central Hospital in Richmond Hill, Ont.

"The blood safety system in Canada is one of the best in the world precisely because we take careful measures," said Julia Hill, director general of the biologics and genetic therapies directorate at Health Canada.

"We are simply saying that there is a theoretical risk, so why take the chance? It's a temporary deferral."

Canadians are very responsible, she said, and don't donate blood when they aren't feeling well or when they're concerned they may have been exposed to viruses of any sort when they are travelling.

"So in a sense, we're really stating what is the obvious to most Canadians," she said, adding that going without these donations won't put any undue stress on the system.

Health Canada reported Thursday a cumulative total of 253 probable and suspect cases of SARS in six provinces, up from 242 the previous day.

The number of cases rose from 195 to 206 in Ontario on Thursday, with a total of 54 people discharged from hospital since the outbreak began.

"The new cases that we're talking about today are, of course, a disappointment," said Dr. James Young, Ontario's commissioner of public security.

"We would rather see our numbers at zero. . . . I think the encouraging thing out of the figures today is that we're not seeing a particular area such as another hospital being involved."

Besides the two Toronto-area hospitals that have been isolated in recent weeks, Stephen Leacock high school was closed Wednesday with teachers and students told to isolate themselves for 10 days, and a Hewlett-Packard plant in Markham, Ont., had 197 of its workers quarantined.

A second Toronto school, Albert Campbell Collegiate Institute, will be closed Friday because of community concerns about the decision to quarantine some students and a staff member. It will reopen Monday.

Meanwhile, officials in York Region, north of Toronto, are in contact with police to look into the possibility of charges being laid against someone who flouted an order to remain in isolation.

In Singapore, 490 people are under home quarantine due to SARS, and the Health Ministry there plans to install monitoring cameras - to be checked at random - in some homes.

"Anyone found breaking the quarantine will be served a written warning and given an electronic wrist tag," which will alert officials if they leave home, the ministry said.

Severe acute respiratory syndrome has killed 10 people in Canada in a little over a month, all of them in the Toronto area.

Concerns also surfaced Thursday in Waterloo Region, west of Toronto, about a probable case of SARS in a young girl who had recently been with her family in China. As well, a woman who's a suspected case was hospitalized in Listowel, Ont., after returning home Monday after two weeks travelling in China. Both were in stable condition.

Gully said airlines at Toronto's Pearson airport are now asking departing passengers whether they've read health alert notices about SARS available at the terminal.

Incoming passengers from Hong Kong, Singapore and on the Air Canada flight from Beijing are receiving yellow SARS cards, and by the middle of next week people arriving on all other flights from Beijing, Shanghai and Taipei will also receive the cards.

"After that, we intend to work toward including all flights from Asia," Gully said, adding that the cards make these passengers aware of SARS information and provide officials with contact information in the event that they need to be traced.

Prime Minister Jean Chretien had lunch Thursday in one of Toronto's Chinatowns to deliver a message of tolerance in the midst of fears about SARS. Some Asian restaurants have experienced a serious decline in business, which they blame on the fact that the disease was introduced to Canada from Southeast Asia.

"We just thought it was the right thing to do," Chretien said, leading a coterie of officials into a restaurant. "Because there is no danger. . . I wanted to give an example."

The World Health Organization reports at least 111 SARS deaths around the globe.

The United States has 166 cases in 30 states under investigation, but no deaths, said Dr. Julie Gerberding, director of the Centers for Disease Control and Prevention.

Meanwhile, a federal funding agency announced a $500,000 initiative to support research on the causes and consequence of SARS.

The Canadian Institutes of Health Research and its Institute of Infection and Immunity, based at the University of Western Ontario in London, Ont., are asking for proposals from researchers by April 25.

The goal is to analyse blood and tissue samples, look at various interventions, develop a rapid diagnostic test and study the immunity of people who have had SARS.