The unidentified medical student, who began working on Mount Sinai Hospital's labour and delivery floor Tuesday, assisted in two deliveries before becoming ill, said Dr. Donald Low, the hospital's chief microbiologist and a leading figure in the city's fight against severe acute respiratory syndrome.

"He may have exposed patients, and obstetrical patients, to this virus," Low said outside the hospital yesterday. "There are five women that we are concerned about that had significant exposure."

But Dr. James Young, Ontario's commissioner of public safety, said there's no real reason for concern.

"The risk to patients and staff is minimal, if there's any risk at all," Young said.

Although Mount Sinai closed its obstetrical unit after the potential exposure, officials stress it's because of staffing shortages and not for fear of further SARS exposure.

Although the student doctor developed symptoms of SARS — a headache and fever — after his 10-day quarantine expired, there are no plans to extend the quarantine period for others, health officials say.

"World opinion still remains (that) 10 days is the correct time," Young said. "But everyone acknowledges there could be outlying cases slightly beyond the 10 days."

While the World Health Organization and local experts are considering the matter, Young added, "we believe currently the 10 days is the correct length of time, and it's the figure we continue to use and rely on."

Although Ontario's SARS containment leaders have debated the issue in past, they argue it's hard enough to persuade someone to quarantine themselves in their homes for 10 days and some people might refuse to comply with a two-week order.

And, Young said, there's no real reason to extend the period.

"The vast, vast majority of cases fall within the 10 days, and there's really a risk in going beyond and extending quarantine periods," he said, because compliance "will diminish."

The latest development left new parents at Mount Sinai concerned and frustrated.

Melissa Tucker, 22, who gave birth to her first child, Montana, on Wednesday, said hospital staff questioned her yesterday about what contact she might have had with the trainee.

All visitors to the seventh floor had to don masks, gloves, robes and goggles as soon as they got off the elevator, said Tucker's husband, Ryan Tobin, 26.

Lesley Matthews and her husband Syd Pell left hospital yesterday with their new baby, Allie, wearing masks. They had spent the day waiting for information while the hospital staff "figured out how to deal with it."

Matthews first heard about the situation when she received a letter from the hospital around 7:30 a.m. yesterday.

Matthews and Pell said they feel bad for the medical student, with whom they were in direct contact. "He is a great guy," said Matthews, adding, "The student was in his 20s. I feel sick for him, we're all fine."

The North York couple have been ordered into quarantine until next Friday and will have to sleep and eat separately. Health officials yesterday said the number of probable hospitalized SARS cases now stands at 69, up four from Thursday. Of those, 21 are in deteriorating condition. Toronto currently has 70 active probable SARS cases, including five patients still struggling to recover from the city's first SARS outbreak. Another 864 people are in home quarantine, including 119 health-care workers — 60 from Mount Sinai.

The disease has claimed 31 lives in the Toronto area; worldwide some 775 are dead of SARS.

The hospital, the city's foremost facility for high-risk mothers and newborns, is home to some of the country's leading neonatal specialists. Closing its obstetric ward, after a similar closing at North York General, will have a ripple effect on maternity wards across the city.

Young said obstetricians and pediatricians are redistributing women scheduled to give birth at Mount Sinai to other hospitals; anyone who was slated to give birth at Mount Sinai is asked to call 416-586-3210.

Of the five women deemed at risk yesterday, three have been discharged and are in home quarantine with their newborns, the other two are in hospital, where one has yet to give birth.

None have shown symptoms of SARS, health officials said.

Another 20 women who have given birth at Mount Sinai — and had minimal exposure to the trainee — will be sent home and told to monitor their health for 10 days, and take their temperature twice a day. There are no restrictions on breastfeeding.

"We hope the babies aren't affected," said Mount Sinai's Low. "We'll monitor that over the next 10 days."

But, Low said, the mothers and babies will be isolated from the rest of their families.

The women and infants were all on Mount Sinai's 7th floor obstetrics ward. The student doctor had worked at North York General in late May and went into quarantine after a recurrence of SARS there. He emerged from quarantine and returned to work at Mount Sinai's obstetric ward Tuesday. He isolated himself after developing symptoms — a headache and fever — on Wednesday, and was assessed as a suspect SARS case on Thursday.

Nevertheless, Low stressed, "we think the risk is very low."

With files from Cynthia Lee

and Karen Palmer