A man in his 40s who worked at a Superstore in Oshawa has been confirmed as the latest person to die of COVID-19 in Ontario, health officials said Thursday.

His death brings the provincial COVID-19 death toll to 15.

Earlier in the day, an Orillia woman was confirmed as the province’s fourteenth COVID-19 death. The Muskoka-Simcoe District Health Unit said the woman, who was in her 70s, died in hospital on Tuesday.

The public health unit believes she contracted the virus from someone in her community.

Ontario health officials confirmed 170 new COVID-19 infections in the province on Thursday morning.

The province now has 835 active cases of novel coronavirus infection, eight clinically-confirmed recoveries and 15 deaths.

The new numbers come as Ontario’s chief medical officer of health Dr. David Williams said Thursday that he wouldn’t be surprised to see the daily number of new cases rise above 200 in the coming days as testing ramps up and as some people return from March Break travel.

Williams said this is “a critical time” to strongly stick to social distancing practices and tougher policies for travellers.

"My main message is to stay home, stay focused on what your distancing is, stay healthy, stay the course," Williams said in a news conference. He added that he's confident that Ontarians "are taking this seriously."

Thursday marked the first day that Canadians returning from abroad are subject to a mandatory 14-day isolation period under the Quarantine Act.

Steepest increase so far

Thursday’s count marks the highest daily increase in active cases reported by Ontario since the outbreak reached the province on Jan. 25.

Officials disclosed 100 new cases on Wednesday and 85 on Tuesday.

The new cases include 12 patients who have been admitted to hospital Intensive Care Units, including a man and woman who are both in their 20s.

Of the 29 people who are currently hospitalized in Ontario, 20 are on ventilators or intubated for assistance with their breathing, health officials said. Bottom of Form

Thirty-five of the new cases reported Thursday were attributed to travel abroad, while fifty-six cases were believed to be tied to close contact with a previously confirmed case.

The cause of all remaining cases was still under investigation.

Community transmission suspected in a quarter of investigated cases

Of all the Ontario cases where investigations have been completed by public health units to date, 60 per cent of patients had travelled within the previous 14 days before becoming ill and 15 per cent had close contact with a confirmed case.

Dr. Barbara Yaffe, Ontario’s associate chief medical officer of health, said that of all the cases investigated by public health officials so far “25 per cent had neither a history of travel, or contact with a close case. So they were likely acquired in the community through community transmission.”

Yaffe said health officials have investigated approximately 60 per cent of all lab-confirmed cases in the province.

New cases confirmed around the province

Of the 124 new cases where identifying information was provided Thursday, 22 are from Toronto, 12 are from Peel Region, 31 are from York Region, five are from Durham and one is from Halton.

Sarnia-Lambton reported its first five cases, all five of which are patients aged 60 to 80+ who were admitted to hospital.

Simcoe-Muskoka Public Health reported four new infections, while Ottawa reported five, Waterloo reported three and Niagara reported two.

Hamilton disclosed one new case while Peterborough reported three new infections.

Haliburton-Kawartha-Pineridge, an area already dealing with a nursing home outbreak in Bobcaygeon, reported 14 new cases, and public health units in northern Ontario reported three new cases.

London-Middlesex reported four new cases, Grey-Bruce reported one and Oxford County reported two new infections.

Close to 11,000 people remain under investigation awaiting test results, the highest number in that category since the outbreak began.

Ontario laboratories were able to turn around 2,439 test results since Wednesday, a slight decrease from their output in the previous 24-hour period.

Premier Doug Ford said Thursday that there are 72 assessment centres up and running across Ontario.

To spare precious tests, Ontario will soon begin using a new definition of recovery that does not involve confirmation through testing.

It is believed the new definition, where a patient is considered recovered 14 days after the onset of symptoms so long as they no longer feel ill and were never hospitalized, will rapidly increase the number of cases counted as recoveries in Ontario.