Western University is assuring students, faculty and staff that "there is very low risk to the campus community," after one of its students who was asymptomatic and at first tested negative, was later confirmed as Ontario's third case of coronavirus.

Dr. David Williams, the province's chief medical officer of health, said the patient is a woman in her 20s who flew from Wuhan on Jan. 23, returning to her home in London by car where she is a Western University student.

Health officials said she did not show any symptoms and wore a mask during the flight and in the vehicle, yet still chose to put herself in isolation.

"We do have a case here where both the system worked well and also, you had a patient who went above and beyond to protect the public and the people she was in contact with," said Dr. Chris Mackie, London's chief medical officer of health.

The patient later admitted herself to University Hospital after showing symptoms, where she was swabbed and sent home.

"As noted ... the student took great care and responsibility by self-isolating at home and seeking appropriate medical attention and has not been on Western's campus since returning to London," the university said in a written statement.

The case is considered unique because the patient tested negative for coronavirus after that first swab. A few days later, a second test showed a "low viral load."

"This is part of the science for the way we develop rapid new tests for a pathogen that we're just learning about," said Dr. Vanessa Allen, chief of medical microbiology at the Public Health Ontario Laboratory.

The patient has recovered to stay in regular contact with the Middlesex-London Health Unit.

We do have a case here where both the system worked well and also, you had a patient who went above and beyond. - Dr. Chris Mackie, London's chief medical officer of health

All cases being investigated by the province are tested at least twice, and so far, no other patient has had a negative test reversed.

The risk for the public remains low, Williams added.

Hospital protocol

"LHSC's Emergency Department team took the necessary precautions to ensure the safety of other patients, visitors, staff and physicians," said Dr. Michael Payne, medical director for infection prevention and control at the London Health Sciences Centre, in a statement online.

The London Health Sciences Centre has been screening patients with symptoms at various points of entry throughout the hospital.

Western University says the risk to the campus community remains very low. (Paula Duhatschek/CBC)

University warns against sharing unverified information

Meanwhile, Western's joint statement from the presidents of the university, students' council and society of graduate students, urges calm.

"Posting and sharing unverified information via social media is not helpful and can contribute to the spread of misinformation and fear," the statement reads.

"As a community, we have to work together to prevent the rise of racism that occurred during the 2003 SARS outbreak. Just as our medical community learned from SARS, our social community must as well.

"The best thing each of us can do right now is to remain calm and approach our peers and colleagues with empathy and kindness," it continued.

Total cases rise to 4

There are now four cases of coronavirus in Canada: three of them confirmed and one presumptive.

Earlier on Friday, the patient with Canada's first confirmed case of coronavirus was discharged from a hospital in Toronto, send home to stay in self-isolation.

The man was being treated at Sunnybrook Health Sciences Centre after arriving on a flight from China last week.

His wife also has a confirmed case of the virus, although she has been at their home in self-isolation. Public health officials said Thursday that she is "doing well" and hasn't shown symptoms of infection.