TORONTO -- Ontario health officials have confirmed the fourth case of coronavirus in Canada and the third in the province.

Ontario’s Chief Medical Officer of Health said that a woman in her 20s, who had a travel history to Wuhan, China, returned to Canada on Jan. 23 on a plane before travelling to London, Ont. in a vehicle.

“At the time, she was asymptomatic,” Dr. David Williams told reporters at a news conference held Friday afternoon. “During her time in her own location she noted some symptoms and did the correct thing.”

“Throughout this time, protocols and procedures were followed excellently in such a way that there has been no risk at all to Ontarians or the health system in this process.”

Williams described the case as “very different” from the other three already confirmed in Canada, as the woman originally tested negative for the virus known as 2019-nCoV. A subsequent test at the National Microbiology Laboratory in Winnipeg showed she was “weakly positive” with the illness.

The woman recovered in a few days, officials said, and remains in self-isolation in her home.

According to the Medical Officer of Health for the Middlesex-London Health Unit, the woman went “above and beyond” to prevent the spread of the illness. She wore the equivalent of a surgical mask on the flight and then went into self-isolation, leaving her home only to go to the hospital the following day.

“Because of her awareness of the risks associated with travel to Wuhan, she went straight into isolation in her home,” Dr. Christopher Mackie said. “Every time she had contact with someone in Canada she was wearing a mask.”

Mackie described the illness as “very mild” and said there were low levels of the virus in her sample.

First test was done ‘properly,’ officials say

The first test for 2019-nCoV was conducted a week ago, the chief of medical microbiology with the Public Health Ontario Laboratory said.

“At the time, it was the very best test, it was the original test that we had all been working on collectively,” Dr. Vanessa Allen. “The original test was done well, it was done properly, it was appropriate.”

The second test was conducted a few days later, she said.

The provincial laboratory is using two tests to determine presumptive cases of 2019-nCoV and then a few days later five more tests are applied to the samples at the National Microbiology Laboratory.

“They actually look at slightly different parts of the virus and making sure that it is there and it wasn’t positive on all of their tests, so again validating that we are really trying to move together to get the right answer,” Allen said.

Officials say that all other people who previously tested negative in Ontario have been retested. No further positive cases have been reported.

Patient is student in London, Ont.

The coronavirus patient is a student at Western University, although health officials say she has not been to the campus since she arrived back in Canada.

In a statement released Friday afternoon, a spokesperson said that the individual is being monitored both by public health officials and the university.

A Western student is confirmed to have Novel Coronavirus. The student took great care in terms of self-isolation and treatment, and has not been on campus since returning from China. @mlhealthunit has confirmed there is very low risk to campus community. https://t.co/4rAEGxYC4h — Western University (@WesternU) January 31, 2020

“Since returning to London, Ont. from Wuhan, China on January 23, and before showing any symptoms, the student took great care and responsibility by self-isolating at home and seeking appropriate medical attention,” the statement reads.

“The student has not been on Western’s campus since returning to London, and Middlesex-London Health Unit (MLHU) officials have confirmed there is very low risk to the campus community.”

First Canadian coronavirus patient discharged from hospital

Earlier in the day, the first Canadian hospitalized with 2019-nCoV was discharged from Sunnybrook Hospital in Toronto.

“In discussion and collaboration with our local public health unit, the decision was made to discharge him home to be with his wife. We are not anticipating his condition to worsen,” Dr. Jerome Leis, medical director of infection prevention and control at Sunnybrook, told reporters earlier in the day. “I think we have been very cautious throughout the process and he seems to be on a clear trajectory of improvement.”

The patient, a man in his 50s, was hospitalized on Jan. 23 the day after he returned from a trip to Wuhan, China. His wife, who travelled with him on China Southern Airlines Flight CZ311, is Canada’s second coronavirus patient.

The woman has been self-isolated in her home and both patients are being monitored by Toronto Public Health.

Toronto’s Medical Officer of Health said in a statement she was not surprised to learn of a third case of 2019-nCoV in the province, but it “does not change the situation in Toronto.”

“We have a very mobile population, with a lot of travel between Canada and China, so it is not surprising to learn of this news today. Local public health officials in London are following up directly on their case. This news does not change our situation in Toronto as we have no new cases here in our city. I will let you know directly if this changes. I want to remind Toronto residents that, at this time, the risk to our community remains low.”

The third Canadian case of 2019-nCoV was confirmed in British Columbia.

On Thursday, the World Health Organization declared the outbreak a global emergency. Close to 10,000 people have been diagnosed with the virus worldwide amore than 200 people have died in China.