Toronto — Toronto may have managed to put a lid on the newest outbreak of SARS, stopping the disease before it was able to spread its tentacles far into the community.
Dr. Donald Low, chief microbiologist at Mount Sinai Hospital and among the most cautious about suggesting severe acute respiratory syndrome has been conquered, said yesterday that he believes Toronto has seen the worst of the current outbreak.
Meanwhile, Barbara Mederski, the head of infectious diseases at the Toronto hospital where the new cluster of SARS cases originated, warned that the virus may be in the general population and can't be suppressed long term by current control measures alone.
Dr. Low said that although there was a large increase in SARS infection over last weekend, especially among health-care workers at the city's emergency departments, "that has dropped off quite dramatically in the last two days."
A Mexican television crew wear masks to protect against SARS while filming outside North York General Hospital Thursday. (J.P. Moczulski/AFP)
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The latest cluster, which began when the virus survived under the radar of public-health officials for more than a month, accounted for 33 probable cases yesterday, up from eight the day before. In addition, there were 29 suspect cases and 107 people who displayed some symptoms and were placed under investigation.
The large rise in probable cases can be attributed, in part, to the fact that Health Canada changed its definition of a probable case yesterday to conform to that of the World Health Organization.
Still, the number of people being investigated doubled. But Dr. Low said he sees the crisis subsiding.
There will be more cases, he said. It will spread within families, appear in hospital visitors, and could yet turn up in patient transfers.
But "the wave that we've experienced this weekend and including Monday night, that wave is behind us."
The number of people in quarantine in Ontario rose to 7,026 yesterday from 5,000 the day before.
Ontario's Chief Medical Officer, Colin D'Cunha, said the large number of students who were isolated after possible exposure at a north Toronto high school and at a liquor store in nearby Aurora was the reason for the spike.
Dr. Mederski, of North York General Hospital, said yesterday that there are people who have mild cases of the disease — some display no symptoms whatsoever — but carry the SARS virus and, in rare cases, could spread it to others.
"Although the epicentre of the infection, at least in Toronto, may have stemmed from a hospital base, the subsequent expansion of that illness in my opinion has undoubtedly gone far beyond clinical institutions and may be in the community, but in a much softer form," she said.
During the first few weeks of the outbreaks, she had several clusters of patients, or individual patients, "whose only contact was an individual who was in the epicentre of the [Scarborough] Grace Hospital and who, for all the world, should have become infected, but who never declared symptoms."
All of these cases were brought to the attention of health and scientific experts, she said. "And in the end, they were stated not to be SARS, even though physicians who dealt with them in my hospital and others felt absolutely and firmly that they fit the clinical pattern."
It's an observation that has been repeated both in Hong Kong and the United States, she said. In Hong Kong, she added, new scientific research shows that people who have had the disease can remain infectious long beyond the 28-day period from the onset of symptoms that is currently accepted as the course of the disease here, and by the World Health Organization.
But Dr. Mederski stressed that she does not believe that community transmission is to be feared. Instead, she said, it is time to put SARS in the same category as other serious viruses, such as influenza, and understand that most healthy people survive.
"As soon as you suggest that it's out there, everybody will panic, they will be fearful and I am suggesting exactly the opposite; that we will now be in a position to say, like many other illnesses, many people get it, very few become very severely diseased."
Since the start of the disease, health officials who have been assigned to contain it have assured the public that all infections in the Toronto area can be traced to a single case that arrived from Hong Kong. They have also said that only people who are in the full throes of symptoms can spread it.
James Young, Ontario's security commissioner, said yesterday that from what he and his colleagues have seen, SARS just "doesn't seem to have legs in the community, it doesn't do well in the community."
It may be difficult to establish links to known cases with each infection, he said, but they exist.
And Frank Plummer, the head of Canada's national microbiology laboratory in Winnipeg, said he too has seen no evidence of people without symptoms transmitting the infection.
But he agreed that there is evidence that the SARS coronavirus is out in the community; his group is planning a study of asymptomatic carriers.
"It's a top priority," Dr. Plummer said.
Dr. Mederski said a number of doctors join her in questioning the traditional thinking about this disease, which suddenly appeared in Canada three months ago.
The new cluster can be traced to a 96-year-old pelvic-surgery patient in the orthopedic ward of North York General who became infected in mid-April. To this point, however, no one has been able to determine how he caught the disease.
"The missing link," said Dr. Mederski, "begs the issue of someone or something that was carrying the virus without the symptoms declaring themselves openly enough to track it, but was still there as an infection component."
