Health officials in Toronto had been hesitant to label five new cases at St. John's Rehabilitation Hospital as SARS because they have been unable to establish a link with a known case of the disease. Last night, information emerged that could firm up a connection.
Grim-faced government officials and doctors said that a patient who was transferred to St. John's had been exposed to a person at North York General Hospital who is now believed to have had severe acute respiratory syndrome.
It is unclear where that initial patient, who has since died, contracted the disease.
St. John's, in the city's far north end, was thrust into the spotlight on Thursday with news that four people who had been at the hospital were under investigation for SARS.
That number has since grown to five, although the SARS diagnosis cannot be conclusive under WHO guidelines without a link to a proven case of the respiratory illness.
At a press conference last night, Donald Low, chief microbiologist at Mount Sinai Hospital, said the female patient transferred from North York probably introduced SARS to St. John's. Three of these five patients are are in critical condition; the other two are considered stable.
Before being transferred, the woman from North York General had shared a ward with a 96-year-old patient recovering from a broken pelvis. That person had exhibited signs of what was believed then to be routine postoperative pneumonia but was probably actually SARS; the patient died on May 1.
The transferred woman went to St. John's on April 28 and within days was displaying SARS-like symptoms.
However, without known connections to a proven case of the disease, she was not treated as a potential SARS case. She is believed to have passed the disease to a health-care worker at St. John's.
There is no evidence that the worker failed to follow proper procedures, but that person is nonetheless believed to have passed SARS on to a pair of patients who were sharing a room.
One of these four people -- it is unclear who -- is believed to have passed the disease to a visitor at St. John's. There is not believed to have been any community spread.
However, in investigating the five cases, officials discovered a cluster of previously unknown cases of SARS at North York General.
St. John's remains under strict infection-control procedures, as does North York General. Hospital emergency rooms across the city have been asked to return to strict SARS procedures. Even so, it is unclear whether this new spread has been stopped, Dr. Low admitted.
"It's so fluid right now," he said. "We're assuming the worst. There has likely been transmission to health-care workers. There has been transmission to family members and there's probably been transmission to other patients."
Dr. Low rejected suggestions that procedures were not followed correctly, or had been too lax. "This is an unusual event," he said.
He said that procedures worked as they should have, even though Toronto is now faced with possibly as many as 30 new cases of SARS.
The officials said last night that many questions remain, and it remains possible that some of these cases will not turn out to be SARS.
The situation is developing so rapidly that Tony Clement, Ontario's Health Minister, acknowledged last night that he was learning some of the developments by listening to his own press conference.
Oliver Moore