A man in his 70s who had travelled to the United Kingdom is Toronto's first death related to COVID-19.

In a news release, Toronto Public Health (TPH) said the man was tested at a hospital in the city and began self-isolation at home. The hospital reported the case to TPH and a case investigation was completed.

The man later presented himself at Trillium Health Partners - Mississauga Hospital on March 14 and died on Saturday, TPH said.

"Today is a very sad day for us and especially the family and loved ones of the man who passed away. We extend our sincere condolences to the family and friends of the individual who died this weekend.

"I'm asking everyone again to make every effort and take every opportunity to practice social distancing. Please stay home, stay safe and take care of each other," Dr. Eileen de Villa, the city's medical officer of health, said in a statement.

De Villa said on Friday that she’s “confident” that Toronto is seeing community transmission of the novel coronavirus.

It is the fourth COVID-19 related death in Ontario. A few hours later, a fifth COVID-19 death was reported in Markham, making it York Region's first coronavirus fatality. A Markham woman in her 70s died on Saturday after returning from Los Angeles, York Region health officials said.

Ontario's first coronavirus fatality was a 77-year-old man from Barrie who died on March 17. Two days later, a Milton man in his 50s became the province's second COVID-19 fatality. A close contact of the first fatality, a Barrie man in his 70s, died on Saturday due to the virus.

As of Sunday, TPH said there are 220 confirmed cases in Toronto, 27 more than the cases reported on Saturday.

Mayor John Tory said the death is a tragic reminder that the world is confronting a deadly virus.

"That is why it is so important that we all continue to do everything we can to stop the spread of COVID-19," Tory said in a statement. "Our medical experts have been clear, everyone has to change their behaviour and stay away from people to save lives."

TPH said they are actively following up with the individuals and their close contacts.

Ontario confirmed 48 new cases on Sunday, bringing the total to 425. In Canada, there are more than 1,400 COVID-19 cases.

Frontline workers test positive for COVID-19

At least 13 healthcare workers have tested positive for the virus, Toronto's Acting Director of Communicable Disease Control and Associate Medical Officer of Health.

"It is important to note that as the situation evolves, it is expected that this number will continue to change daily," Dr. Michael Finkelstein said in a statement.

The individuals who contracted the disease worked at a hospital, community healthcare, and long-term care.

He said the public needs to adhere to public health's advice of limiting social interactions as much as possible to protect essential city services.

Finkelstein said healthcare workers should closely track how they feel and identify themselves to their manager if they feel unwell.

People react differently to the virus

Infectious disease specialist Dr. Isaac Bogoch said the two new deaths show how the novel coronavirus exhibit differently in people.

“You can have the same infection and it’s going to have very different manifestations on different people,” Bogoch said.

The Toronto man had a protracted battle against the virus compared to the Markham woman who had an acute illness.

Bogoch said it relates to how the virus interacts with a person’s immune system and a person’s immune response to the infection.

The rise in COVID-19 cases means that there is a lot of virus transmission in community settings, Bogoch said, adding that many have mild symptoms.

“They might not feel sick enough to seek medical care. They might not even think that they have this virus. These are people walking around and possibly transmitting it to other people,” Bogoch said.

He said it is crucial for the public to adhere to the guidelines of physical distancing.

“For the most part, many of us are going to be okay. It’s just our more vulnerable population like the elderly are going to have a much more challenging course with this virus.”