Two recent deaths in a Toronto hospital may have been caused by SARS and more than 20 other people may have been exposed to the virus, provincial officials said Friday.
"We are assuming the worst," said Dr. Donald Low, director of microbiology at Mount Sinai Hospital.
If the cases turn out to be SARS, they will signal the resurgence of the virus in Canada's largest city.
Canada is the country outside Asia that has been hardest hit by SARS, with 24 deaths since its outbreak in March. All the deaths have been in the Toronto region.
Health officials on Friday were investigating the source of five new possible cases of SARS, Canada's first new cases in over a month.
The World Health Organization said it would keep Toronto off its list of SARS-affected areas, saying these new cases were still under investigation and could not be considered probable.
The US Centers for Disease Control and Prevention (USCDC),however, on Friday recommended putting off any non-essential travel to Toronto.
The USCDC alert recommends that US travelers to Toronto take precautions to safeguard their health and avoid settings where there has been evidence of transmission of severe acute respiratory syndrome. Is does not advise that Americans postpone or cancel trips to the city.
The two victims suspected to have died of SARS, 96 and 80 years of age, were treated at the North York Hospital in Toronto, Low said.
He asked the 20 or so people who may have been exposed to the virus to isolate themselves.
"We are assuming the worst, that there has been a likely transmission to health care workers and that there has b`een transmission to family members and there has probably been transmission to other patients," Low said.
Of the five new cases under investigation, three of the patients are in serious condition, Ontario provincial Public Health Commissioner Colin D'Cunha said.
Toronto's Associate Medical Officer of Health Barbara Yaffe could not say if the five new cases were linked by a common source of infection.
"It is not clear what the source of the infection was," she said.
"What we are clear about is that it was not community-acquired. It is either travel-related or health care-institution related," she told reporters, noting that one of the individuals returned from China last last month.
But in Ottawa, a senior director for the federal agency Health Canada, Paul Gully, told reporters there was no evidence that the new cases were travel-related.
The last new "probable" SARS case in Toronto was recorded April 19, Gully noted.