Ontario reported 538 new cases of COVID-19 on Thursday and three new deaths, with Toronto still accounting for nearly half of all new infections.

"Locally, there are 229 new cases in Toronto with 101 in Peel, 66 in Ottawa and 43 in York Region," Elliott said on Twitter. "(Sixty per cent) of today’s cases are in people under the age of 40."

The province reported 625 new cases on Wednesday, 554 on Tuesday and a record-setting 700 on Monday.

Provincial labs processed 39,600 test specimens, up from 35,753 one day earlier.

Thursday's tests generated a positivity rate of 1.36 per cent.

There are now 82,473 test specimens awaiting processing, or equivalent to about two-days' worth of the province's maximum daily processing capacity if no other tests were added.

NDP leader Andrea Horwath slammed the testing backlog on Thursday.

"In Ontario, 82,473 people are waiting for their test results. They can’t go to work. They’re at home with kids who can’t go to school," she said. "It didn’t need to be this way. We should have been investing in public health rather than Ford's cuts. We need public health investment now."

Health officials have said daily testing capacity will hit 50,000 in the next few weeks, with an increase of up to 78,000 per day called for in the Ford government's fall preparedness plan.

Elliott said that it is imperative the backlog clears soon because unprocessed specimens will start to spoil.

"The specimens are only good for three days and then they spoil and people have to be re-tested," she said.

She said several university laboratories in Hamilton, Guelph and London were coming online to help process tests.

When asked if all specimens currently in the hands of Ontario labs would be processed before they expire, Chief Coroner Dr. Dirk Huyer said everything was being done to speed up processing of results.

"I'm not in a position to answer it from the perspective of a guarantee," he said Thursday afternoon. "All steps are being taken to do the testing as quickly as possible and as effectively and efficiently as possible."

Associate Chief Medical Officer of Health Dr. Barbara Yaffe said the backlog is more evidence people should heed the latest guidance on testing and not seek a test unless it is necessary.

"That is one of the reasons we are saying don't get a test unless you need it," she said. "You will just add to the backlog and it is very important that the test is done in a timely fashion."

A total of 515 people recovered from infection on Thursday, leading to a net increase in active cases of 20.

There are now 4,975 remaining active cases of novel coronavirus infection in Ontario, up from less than 900 in late July.

According to local public health units, a total of 2,866 people have died of COVID-19 since the pandemic began in March.

Public Health Ontario said two of the three deaths reported Thursday occurred in long-term care homes. All details of the third death were not disclosed.

Yesterday, provincial health officials released new modelling suggesting the province could see as many as 1,000 cases per day by early to mid-October.

Even so, the Premier said Wednesday that now was not the time for a return to Stage 2 of reopening, which would end activities such as indoor dining, cinema-going, bar attendance and exercising in gyms.

Speaking on Thursday, Ford said he had no imminent plans to reverse things such as indoor dining, but surging cases numbers could change everything.

"Everything's on the table and if you asked me in four days if the cases were up over 1,000 things could change but not right now, we just want everyone to continue to follow the guidelines," he said.

UHN epidemiologist Dr. Isaac Bogoch told CP24 it is likely new measures beyond what has already been enacted in the province will be necessary to lower the case count.

"We know what can happen in the next two weeks and then the weeks and months ahead, it's never too late to pivot, to turn around when you're going down the wrong path and we can certainly adopt strategies to get this under control."

Elsewhere in the GTA, Halton Region reported 3 new cases, while Durham Region reported 14.

Hospitalizations continue to rise across the province, with 162 people receiving treatment for COVID-19 on Thursday, up from 150 on Wednesday and 88 at this time last week.

Of those, 36 patients are in intensive care and 17 of them are breathing with the help of a ventilator.

Health officials said Wednesday it would be difficult to maintain the pace of all regularly scheduled surgeries with 150 patients in intensive care and "impossible" once 350 ICU beds are occupied by COVID-19 patients.