Ontario’s top doctor says that we are in a “race against time” with COVID-19 variants now making up nearly a third of all new cases.

More than 31 per cent of all positive cases in Ontario last week screened positive for a variant of concern, up from 18.9 per cent the week prior.

The rapid rise in the proportion of cases involving new variants has prompted concern about a potential third wave, especially given the fact that the more infectious B.1.1.7 variant has made up the vast majority of the cases.

“We are in a race against time here. We are getting more vaccines and we want to vaccinate as quickly and as many (people) as we can as many as we can but that will take time,” Chief Medical Officer of Health Dr. David Williams said during a briefing on Monday afternoon. “If we just hold and be firm and be careful for the next couple weeks we can keep even the variants I believe under control, bending the curve from that rapid rise. But there is a sense that it (case numbers) will go up. We just want to make sure that it is not too much and doesn’t compromise our healthcare system.”

The stark warning from Williams on Monday afternoon came a few hours after Ontario reported another 1,631 cases of COVID-19, which was the highest single-day tally since Feb. 5.

Officials, however, later said said the spike was due to data management issues with the province's coronavirus contact management system.

The province reported 1,299 new cases on Sunday, 990 more cases on Saturday and 1,250 new cases on Friday. Williams, however, said that the data delay likely means that those numbers should have been higher.

“We are in this phase where the model is saying we could be trending up back again and we have seen our variants of concern taking up more and more the percentage of cases day by day. So our concerns are there,” he said. “We need to remain vigilant.”

Across the GTA, Toronto reported 568 cases, the highest daily total that city has seen since Feb. 5, while Peel Region reported 322 new cases, the highest daily total the region has disclosed since Feb. 2.

York Region reported 119 new cases on Monday, while Durham Region reported 68 new cases, Halton reported 51 and Hamilton reported 22.

Provincial labs processed 38,063 tests in the past 24 hours, generating a positivity rate of at least 3.4 per cent.

None of the ten deaths reported on Monday occurred in the long-term care system.

There are now 11,016 active cases of novel coronavirus infection across the province, up from 10,570 one week ago.

A total of 7,077 people are known to have died from COVID-19, while 291,800 people have made a full recovery from illness.

The seven-day rolling average of daily cases rose to 1,155 on Monday, up from 1,069 on Sunday.

Meanwhile, hospitalizations stayed relatively flat when compared to Sunday.

The Ministry of Health says there were 626 people in hospital on Monday, up 20 from Sunday.

Of those, 282 were in intensive care and 184 were breathing with the help of a ventilator.

But a count of data from the province’s 34 local public health units and hospital networks found 832 people in hospital receiving treatment for COVID-19 on Monday.

A Toronto ICU doctor citing data from Critical Care Services Ontario said there were 337 people in intensive care due to COVID-19 on Monday.

Public Health Ontario confirmed an additional 63 cases of coronavirus variants of concern in the past 24 hours, bringing the total confirmed through whole genomic sequencing in the province to 935.

There are also several thousand additional positive specimens that screened positive.

The province said it administered another 21,000 doses of approved coronavirus vaccines on Sunday, bringing the total number of shots administered to 912,486.

More than 273,000 people have now completed the full two-dose inoculation.