A police guard has been posted outside the Toronto hospital room of at least one SARS patient to ensure no one breaches exit or entry rules.
In meetings where the agenda is containment of the disease, talk is turning to the use of private-security investigators to patrol around the homes of those under quarantine. Provincial officials are mulling outfitting the housebound with electronic monitoring bracelets.
After a week of disturbing events, officials grappling with severe acute respiratory syndrome are taking few chances with a virus that is proving to be unforgiving and perhaps even more virulent than first suspected.
Missteps have led to the exposure of more than 500 members of a Roman Catholic charismatic group, 1,000 people who passed through a Scarborough family clinic, 450 attendees of a Montreal business conference, and possibly the residents of a 252-unit Toronto condominium building.
Until now, health officials took comfort in the fact that nearly all SARS cases in Ontario had been passed on in hospital settings, or in households of people connected to hospitals. Those cases could be easily traced back to Hong Kong's Metropole Hotel where a 78-year-old Toronto woman and several others caught SARS in February from an infected Guangdong doctor who, as it happens, was staying in room 911.
"The frustrating thing is that we have seen this week something that we hoped would not happen," said Donald Low, chief microbiologist at Mount Sinai Hospital in Toronto. "We have seen the disease go into the community."
In Toronto, the epicentre of Canada's outbreak, SARS has now been transmitted at a funeral home, workplaces, a church, social gatherings, and possibly even within a condominium building.
"We're in a new phase of the illness," Dr. Low said. "We're into the community phase and that has to be aggressively controlled. But it's where we have far less control than we did in a hospital setting."
Success now rests on how quickly health workers can actually track the hundreds of contacts that might have been exposed to SARS and how well those contacts follow the strict quarantine measures.
Any slip could trigger the next phase of an outbreak — the one feared most of all — where efforts to connect a SARS case to an original cluster through an intricate maze leads to nothing more than a question mark.
Sheela Basrur, Toronto medical officer of health, has said the situation has not yet resulted in such sporadic cases, even though health workers have yet to find the link between a new SARS case in the condominium building, where an infected family was already known to have lived.
"If history repeats itself, we will find the link sooner or later," she said.
Lilian Yuan, an assistant professor in public-health sciences at the University of Toronto, compared the situation to being on a "knife's edge."
"We are at a critical moment," said Dr. Yuan, a former associate medical officer of health in Toronto who has been helping with local containment efforts.
"We also know that the incubation period for the disease is 10 days, so the next crop of cases — if there is to be a big one — will come in the next week."
Doctors have been troubled by the speed and severity of the SARS cases in the recent community outbreak.
Dr. Low said one would expect to see severe SARS cases emerge in hospitals, since patients are already sick. Most Ontario SARS deaths to date have involved elderly people battling other ailments.
But, he said, many of the 31 infections that have resulted from the exposure in the Bukas-Loob Sa Diyos religious group are more serious than expected. One of the group's members was first exposed at Scarborough Grace Hospital where Canada's first SARS cases were treated.
Six of the 31 people subsequently infected now rely on ventilators to breathe, Dr. Low said. Yet those infected were relatively healthy with a median age of 40.
Two family doctors who caught SARS after the original infected BLD members were treated at their clinic, are among those in critical and serious condition. Dr. Low said the doctors may have received a massive dose of virus if they were unprotected while examining SARS patients, a theory often cited to explain younger SARS fatalities.
"But it's more difficult to make this [massive dose] argument to explain the cases we have seen from the community transmission," Dr. Low said. "It may be that all it took in some cases was exposure to one virus and wham, it could make the person sick."
One suspicion is that some people may be genetically susceptible to more severe forms of the disease. But the other more alarming possibility is that more virulent strains of this new coronavirus are evolving.
"It wouldn't be surprising to see variations in strains [of the coronavirus]. It is always changing," Dr. Low said. "It's one of the reasons we don't have a vaccine for colds."
Hong Kong, a region that has experienced 1,327 SARS cases, reported this week that several recent SARS deaths included previously healthy men and women in their thirties, forties and fifties.
Lap-Chee Tsui, the famed geneticist who recently left Toronto's Hospital for Sick Children to become president of the University of Hong Kong, said in an e-mail exchange this week that his labs are investigating whether different strains of the new coronavirus named as the cause of SARS already exist.
The halo-shaped coronaviruses are notorious for their chameleon-like qualities. Caroline Astell, molecular virologist at the Michael Smith Genome Sciences Centre of the B.C. Cancer Agency, where the SARS virus was first sequenced last Saturday, estimated that, with every replication, these viruses alter three of their approximately 30,000 nucleotides, the chemicals that comprise their genetic material.
Based on previous bacterial and viral studies, Dr. Low estimates that the virus probably replicates inside its human host every 20 minutes, meaning three new generations of the pathogen are produced every hour.
"By the end of the day, you could have a virus genetically different than the one that first infected you," he said.
All the while, Dr. Low explained, a virus might be selecting for its most advantageous form, causing an infection serious enough to propagate itself, but not so serious that it kills its host before it can be passed on.
"People don't appreciate how infectious this is," Dr. Low said. "This thing is so infectious, it's not so surprising to me to see infection even if there has been protection: infection-control measures have to be followed to a T."
With no one known to be immune to the disease and no specific drugs to treat it, Dr. Yuan stressed that just like in the preantibiotic era, quarantines are the only hope of containment.
"We can't break the chains of transmission by any other means," she said.
Dr. Yuan noted that the chances of catching the infection in the general population remain exceedingly low.
If this doesn't seem to jibe with the heightened concern voiced by health officials, Dr. Low said he has only one wish for the month ahead.
"All I want to hear a month from now is how we overreacted."
