TORONTO -- Public health officials have confirmed that a man in his 40s who worked at a Real Canadian Superstore location in Oshawa is the latest COVID-19-related death in Ontario, bringing the provincial total to 15 fatalities.

The total number of COVID-19 patients in Ontario has risen to 858, with health officials announcing 170 more positive cases on Thursday alone.

Ontario's Associate Medical Officer of Health Dr. Barbara Yaffe said 29 of those patients are currently receiving intensive care in hospital, 20 of which are on ventilators to assist with breathing.

Yaffe said that of the cases that have been investigated by public health officials, community transmission is suspected in roughly 25 per cent. However, health officials have only investigated around 60 per cent of Ontario's confirmed cases.

Shortly before provincial health officials updated their response to the spread of the novel coronavirus, the Simcoe Muskoka District Health Unit confirmed a third death in their region.

The deceased patient is an Orillia woman in her 70s.

The other deaths in Ontario linked to COVID-19 were residents of Toronto, Ottawa, Barrie, Hamilton, Lindsay, and Milton.

170 new cases of COVID-19 in Ontario

The 170 new cases announced Thursday include 22 people in Toronto, 33 in York Region, 15 in Peel Region, five in Durham Region, three in Peterborough, and on in Halton Region and Hamilton.

As well, there are five more cases in Ottawa, 14 in Haliburton Kawartha Pineridge, four in Middlesex London, four in Simcoe Muskoka, four in Lambton, three in Waterloo, two in Niagara, two in Oxford, and one in Northwestern, North Bay and Sudbury.

The location of all additional cases is listed as “pending.”

Ontario's Chief Medical Officer of Health Dr. David Williams said that he isn't surprised by the increase in cases, attributing the jump in numbers to Ontario residents recently returning from international travel.

"It’s not surprising that the numbers are rising, we know that more people are coming back from March Break," Dr. Williams said. "Numbers will rise in the next few days again – more people are coming back and lab testing capabilities are ramping up more – those two together mean our numbers could go up and not surprising if it goes up 200 in a day."

Dr. Yaffe said that of those who travelled outside of Canada and tested positive for COVID-19, the United States and Europe are among the most popular destinations.

Fifty-six of the 170 cases are linked to a close contact of a previously confirmed case of the virus, while 35 are linked to recent travel outside of Canada. The rest of the cases all have their means of transmission listed as “pending.”

Twelve of the new patients remain in hospital receiving medical care, including two people in their 20s.

10,000 people under investigation for the virus

While announcing the new cases of the novel coronavirus on Thursday morning, health officials stated that more than 10,000 people are currently under investigation for the virus and more than 26,000 people in the province have tested negative thus far.

In the province, eight people previously infected with the virus have since recovered.

Symptoms of the virus, which can include fever, cough and shortness of breath, are similar to other respiratory infections.

There are no specific treatments for the virus and there is no vaccine that protects against it.

The Ontario government’s website advises those experiencing symptoms of the novel coronavirus to contact their primary health care provider or Telehealth Ontario at 1-866-797-0000.