Ontario has confirmed three new positive cases of coronavirus, bringing the total number of confirmed cases in the province to 11.

The new cases involve a woman, 34, in York Region, and another woman, 51, and her husband, 69, in Durham region. Both women had just returned from Iran.

York Region public health officials have begun a search for anyone who might have come in contact with one of the cases, either in the air or on a GO bus to Richmond Hill.

As of Saturday, there were 20 confirmed coronavirus cases in Canada. The number includes eight in B.C. and one in Quebec. There have been no deaths.

Dr. David Williams, Ontario's chief medical officer of health, said in a news release on Saturday that the first three cases of coronavirus found in Ontario have been resolved, with each of those patients having had two consecutive negative tests at least 24 hours apart.

Of the cases announced on Saturday, the 34-year-old woman "with a travel history to Iran" went to Mackenzie Health, a Richmond Hill, Ont., hospital, on Thursday. York Region Public Health had contacted the hospital and arranged a time for the woman to go to its emergency department.

She was wearing a mask when she arrived at the hospital.

Patients now in self-isolation

Williams said the woman arrived at the hospital with a dry cough, runny nose, shortness of breath and headache and was put on "airborne/droplet/contact" precautions.

"Due to the low severity of symptoms and the condition of the patient, the patient was not admitted to hospital. The patient is in self-isolation, per protocols, where she remains," Williams said in a news release on Saturday.

In the second case announced on Saturday, the 51-year-old woman returned from Iran on Feb. 22 and went to an Ajax clinic on Friday with a cough, body aches and chills. She was masked and isolated.

Durham Region Health Department contacted Lakeridge Health Ajax Pickering hospital and arranged for a time for the woman to arrive.

She arrived at the hospital wearing a mask and was tested for the virus. She was discharged from the hospital, sent home and went into self-isolation, where she remains.

Her 69-year-old husband, meanwhile, also tested positive for the virus on Friday. He had a cough, but did not go to Iran. He accompanied his wife to the Ajax clinic and Lakeridge Health Ajax Pickering, where he was given a mask and isolated. He was tested for the virus, discharged and sent home.

He has also been put in self-isolation, where he remains.

Ontario preparing for 'potential of local spread'

Williams said the Ontario government is carefully monitoring the situation and encourages residents to keep informed on developments concerning the virus.

Dr. David Williams, Ontario's chief medical officer, says: 'At this time the virus is not circulating locally. However, given the global circumstances, Ontario is actively working with city and health partners to plan for the potential of local spread.' (Pierre-Olivier Bernatchez/CBC)

"At this time the virus is not circulating locally," Williams said. "However, given the global circumstances, Ontario is actively working with city and health partners to plan for the potential of local spread."

Worldwide, the number of people sickened by the virus is about 85,000. There have been more than 2,900 deaths, most of them in China.

York region case presents a 'number of complexities'

Dr. Karim Kurji, York Region's medical officer of health, told reporters at a news conference on Saturday that the 34-year-old woman in the first case travelled from Iran with her husband and toddler on Tuesday, with a layover in Denmark. She was not wearing a mask.

He said this particular case presents "a number of complexities" as a result of the woman's travel.

The woman developed symptoms on Tuesday, before her last flight from Copenhagen to Toronto on Wednesday. She took three flights in all.

Kurji said the woman then took a GO bus from Toronto Pearson International Airport, Terminal 1, on Wednesday afternoon. She was travelling eastbound, sitting in the upper deck, and her final destination was the Richmond Hill Centre Terminal.

Dr. Karim Kurji, York Region's Medical Officer of Health, says the case involving the 34-year-old woman involves a 'number of complexities' because she took three flights and was not wearing a mask. (CBC)

People who were on the following flights and the bus may have been exposed to the positive case of coronavirus, Kurji said:

Passengers in the business class section of Qatar Airways flight QR 483 and QR 163 on Tuesday.

Passengers in the business class section of Air Canada flight AC 883, from Copenhagen to Toronto, on Wednesday that landed at 2:55 p.m. at Pearson.

Riders on GO Bus number 40 eastbound and who sat on the upper deck of the bus on Wednesday from Pearson Airport to Richmond Hill Centre Terminal. The bus left Pearson at about 3:55 p.m.

Anyone who was in these areas is urged to contact York Region Public Health at 1-800-361-5653, from Monday to Sunday, between the hours of 8:30 a.m. to 8:00 p.m., for further assessment.

"The individual is currently in self-isolation, recovering at home, as a result of the co-ordinated and collective efforts of our healthcare and public health system," Kurji said. "The individual was quickly recognized, assessed and isolated."

Kurji said York Region Public Health is aggressively trying to trace all close contacts of the woman and people who may have been exposed. York region public health officials are trying to get the flight manifests of the planes on which she travelled.

"There has been a number of areas where exposure could potentially happen," he said.

Kurji said the risk level of exposure is lower on the bus than it would have been on the plane because there is more ventilation, a shorter period of travel and people getting on and off.

600 in self-isolation in York Region since virus appeared

In a news release, the Regional Municipality of York says: "Individuals that were not in direct or close contact with the individual are not considered at risk of becoming infected. The risk to York Region residents continues to remain low and there is no evidence of community spread within York Region."

As for passengers on the GO bus, Anne Marie Aikins, spokesperson for Metrolinx, the provincial transit agency says, "We will work co-operatively with public health authorities to assist in identifying customers on the bus." ​​​​

Since the coronavirus first surfaced, about 600 people within the last two months have been put into self-isolation in York Region and public health officials have investigated a total of 200 people, officials said.

Hospital says it was prepared

Mackenzie Health was prepared to receive a coronavirus case and "all the proper precautions" were already in place when the woman in the first case arrived, according to Dr. Danny Chen, lead in infection prevention and control for the hospital, in a memo to staff obtained by CBC News.

He thanked the emergency department for "promptly identifying and isolating" the person.

"It is understandable that news of a presumptive positive case here at our hospital may cause concern for you. Because of the protocols in place, there were no staff, patient or visitor exposures related to this case," he told staff. "This reinforces the importance and effectiveness of our protocols."

He said staff and patient safety is paramount.

"Although the situation surrounding COVID-19 continues to change and evolve — and more cases of COVID-19 will be identified going forward — what hasn't changed is the fact that we're prepared, and that staff and patient safety will always remain a priority at Mackenzie Health."

According to Chen, York Region Public Health contacted the hospital on Thursday before the person was sent to its emergency department.

Officials worked out a time for the person to go to the emergency department, the person arrived wearing a mask, presented symptoms of coronavirus and was immediately put on "airborne/droplet/contact" precautions, he said.

"A physician assessed the patient and determined that admission to the hospital was not required due to the condition of the patient and the low severity of their symptoms," Chen said.

"The patient was advised to self-isolate until the test results were received and to return if symptoms worsened."

The hospital received confirmation that the case was presumptive on Friday evening, he said. That case has since been determined to be positive.

In a news release on Saturday, the hospital said: "Hospital operations are running as normal."