Dr. Heather Morrison has confirmed a third case of COVID-19 in P.E.I. and is asking passengers on WestJet flight 3456 from Toronto to Moncton on March 16 to self-isolate.

Morrison says the case is a Queens County woman in her 20s who returned from Spain through Toronto.

"We have another example of international travel with our case in P.E.I., and another case where she followed the recommendations and knew about self-isolation," Morrison said.

"Public health has been following up this afternoon with anyone who has been in contact with this individual, and this will continue as we reach out to Ontario and New Brunswick over the evening."

The woman arrived in Toronto on March 14 and self-isolated in a hotel as opposed to staying with friends or family, Morrison said.

WestJet flight 3456

On March 16, the woman flew from Toronto to Moncton on WestJet flight 3456, departing Toronto at 8:35 a.m. and arriving in Moncton at 12:05 p.m. All passengers on that flight are being asked to self-isolate.

P.E.I.'s third case of COVID-19, a woman in her 20s, self-isolated in a hotel for two days in Toronto before flying to Moncton. (Adrian Wyld/Canadian Press)

The woman then travelled to P.E.I. in a car after flying to Moncton. Morrison said she has "very mild symptoms" and had them before arriving in the province.

She went directly into self-isolation upon returning to P.E.I. and was tested March 17, said Morrison.

The chief public health officer said she spoke to the woman this morning and she is at home and doing well.

The first case, a Queens County woman in her 50s who had returned from a cruise, was announced last Saturday. The second case, a Queens County man in his 40s who had returned from the U.K., was announced Thursday.

390 tests on the Island

Morrison hadn't been scheduled to give a news conference Sunday, but said she did not want to wait until Monday to share the information of the third case with Islanders.

As of Sunday, Morrison said more than 390 COVID-19 tests have been conducted on P.E.I. There have been three positive cases, 231 negative and the rest are pending.

She said Canada has over 1,300 cases.

"These social distancing measures, which are really physical distance measures ... we are trying somehow to keep socially connected and emotionally connected," Morrison said.

"People are really reaching out to one another in P.E.I., and I think it is amazing, and very supportive in a very difficult time that we're in."

In Saturday's briefing, Morrison said additional screening protocols were being put in place at all access points to the province, including the airport and Confederation Bridge.

She also said anyone who has travelled outside the province from March 21 onward, even within Canada, has to self-isolate for 14 days. Initially the directive only applied to those returning from international travel.

"If you're returning to P.E.I. from anywhere, out of country or out of province, you need to self-isolate for two weeks," Morrison said during Sunday's briefing.

"However, there are exceptions that are in place for essential workers, truck drivers, airline crews, essential frontline workers in the public and private sector, and workers in critical sectors."

All of P.E.I.'s COVID-19 cases have been travel related.

COVID-19: What you need to know

What are the symptoms of COVID-19?

Common symptoms include:

Fever.

Cough.

Tiredness.

But more serious symptoms can develop, including difficulty breathing and pneumonia, which can lead to death.

What should I do if I feel sick?

Isolate yourself and call your local public health authority. Do not visit an emergency room or urgent care centre to get tested.

How can I protect myself?

Wash your hands frequently and thoroughly.

Avoid touching your eyes, nose and mouth.

Be aware of evolving travel advisories to different regions.

More detailed information on the outbreak is available on the federal government's website.

More COVID-19 stories from CBC P.E.I.