Canadian health officials placed employees at a technology plant in Ontario under quarantine after one worker showed up for work despite showing symptoms of severe acute respiratory syndrome, officials said today.

Authorities said the quarantine order affected employees of a Hewlett-Packard (Canada) plant in Markham, Ontario, near Toronto.

"One individual has caused 197 other individuals to be isolated in quarantine and it has impacted that workplace. It has impacted society in general," said Hanif Kassam, acting medical officer of health in York Region.

Kassam said health officials were in regular contact with the unidentified worker at the factory, who has now been hospitalized and is being treated for symptoms of the ailment, now commonly known by its acronym SARS. Canadian health officials expressed concern that violation of quarantine orders could harm efforts to contain the sometimes-fatal illness.

"We really can't stress enough if someone is in isolation, they must follow the rules of isolation," said James Young, Ontario's commissioner of public security. "If public health says you need to be in isolation, you should be in isolation."

Officials said the case showed the dangers of relying on voluntary quarantine and the potential dangers of spreading SARS, about which little is known. Most SARS cases in Canada have been transmitted, so far, in households or hospitals.

"Our health care system in Canada cannot continue to see prolonged stress placed on it by individuals here and there not following the isolation requests," said Colin D'Cunha, Ontario's commissioner of public health.

Health officials this week closed two schools after a high school student who was supposed to be quarantined at home went in to take an exam. Officials said the girl began experiencing symptoms of SARS shortly after leaving school.

The unnamed girl had been in quarantine for nearly 10 days, supposedly the maximum period required. However, officials have not devised a test for SARS and there are questions about the length of quarantine periods.

Health officials so far have asked more than 3,000 people in the Toronto area to go into voluntary isolation. More than 20 warnings have been issued for quarantine, authorities said.

People in quarantine should remain in their homes, sleep separately from other people in their households and use masks when they are in contact with other family members, health officials said. They said people violating quarantine provisions could face mandatory isolation in hospital wards.

"We can't and will not tolerate people breaching isolation," Young said. "This puts everybody at risk."

Federal health officials reported today there were 253 probable or suspected cases of SARS in the country, 206 of those in Ontario.

World Health Organization officials today reported 59 new cases of SARS worldwide. The number of cases worldwide rose to 2,781, and at least 111 deaths. WHO officials reported at least 1,337 of those who contracted the disease have recovered.

Canadian health officials have warned against travel to Asian countries where cases of SARS have been reported. Meanwhile, officials reported the first probable case in Africa. They said the person suspected of carrying the disease had traveled to Hong Kong recently.