There are now four cases of COVID-19 in Alberta, health officials announced Sunday.

Three cases are presumptive and one has been confirmed.

"All the cases of COVID-19 to date are travel-related and recovering in isolation at home with support from public health officials. As soon as these cases were identified last night, we took immediate action to protect the public," Dr. Deena Hinshaw, the province's chief medical officer of health, said.

Three of the four patients are connected to the same cruise ship. The first of the two new cases is a man in his 60s from the Edmonton zone. He was onboard the Grand Princess cruise ship before it was quarantined off the coast of California. He returned to Alberta on Feb. 21.

The second new presumptive case is a woman in her 30s from the Calgary zone who is a close contact of someone who had recently travelled in Europe. The individual who travelled to Ukraine, Turkey and the Netherlands also lives in Alberta, and officials are awaiting test results to see if that person also has COVID-19.

Hinshaw said health officials learned about the two new cases late Saturday.

'This is an important confirmation'

All infected individuals have been isolated and public health measures are in place to prevent the infection from spreading, Hinshaw said. All four are at their respective homes and are expected to recover. Health officials have been reaching out to anyone who was in close contact with any of the patients.

"Anyone in close contact is being advised to self-isolate for a period of 14 days. Any of these close contacts who have symptoms of fever or cough will be tested," Hinshaw said.

While four cases in four days may seem alarming, Hinshaw said she wanted to underline that three of the four cases were linked to the same cruise ship. The province ran 299 tests for COVID-19, and 297 were negative, she said on Saturday.

The first presumptive case announced last week, a Calgary woman in her 50s, was confirmed by the National Microbiology Laboratory in Winnipeg.

"This is an important confirmation, and validates the test from our province," Hinshaw said.

This illustration provided by the Centers for Disease Control and Prevention (CDC) in January shows the 2019 novel coronavirus. (The Canadian Press)

That woman had been on board the Grand Princess cruise ship before it was quarantined off the coast of California. She returned to Alberta on Feb. 21.

On Friday, Hinshaw announced a man in his 40s who lives in the Edmonton zone tested positive for COVID-19. The man had visited Michigan, Illinois and Ohio before returning to Alberta on Feb. 28.

Hinshaw said it's believed the source of his infection was a travel companion who had been a passenger on the Grand Princess cruise ship, and said that person is now a confirmed case in his home province of British Columbia.

All close contacts who may have been exposed to the virus have all been isolated, and testing is being done on a small number who have potential symptoms, Hinshaw said. She said that man did not attend any large social or public gatherings before entering isolation, which Hinshaw said likely helped limit the spread.

She said she could not share which Edmonton-area community the man lives in because of concerns about identifiability. She said anyone who has been in contact with one of the patients will be personally contacted by public health staff

"People don't need to worry that they may be at risk if they're not contacted," she said.

Health officials learned of the Edmonton case on Friday afternoon, Hinshaw said, and are currently identifying close contacts of the man and asking them to self-isolate at home.

Travellers should isolate themselves if sick

Hinshaw said the province's approach to monitoring the virus is going well but she said it is important for all travellers returning from outside Canada to be vigilant, and to quickly isolate themselves and stay home if they develop a fever or cough.

"While most people who catch this virus have a mild illness, it can be severe or even deadly for our elderly or those with medical conditions. In some cases, even otherwise healthy people can get sick from this virus," she said.

There is not yet a vaccine or treatment for the illness and unlike influenza most people do not have any immunity to it. Unlike measles, it doesn't spread through the air. It can spread person-to-person through droplets in coughs or sneezes, or by touching a contaminated surface and then touching one's eyes, nose or mouth.

Hinshaw said the risk of exposure in Alberta remains low, and said the risk could be upgraded if there is exposure outside the known travel-related cases.

Hinshaw said the province is updating its website Sunday with tips and resources for managing risk of the virus

"Rather than cleaning the stores out of toilet paper, probably what would be helpful is talking to neighbours, talking to family and friends, about if anyone in that community circle needed to stay home for two weeks, who could help support them by getting supplies," she said.