Hope is in the air as Toronto's vaccine rollout gets underway and non-essential retail stores reopen under grey zone rules, but the city's Medical Officer of Health warns that some of this optimism may be unfounded — or at the very least that it should be tempered with caution.

"While we are doing everything possible to vaccinate Toronto as quickly as possible, I want to thank Torontonians for continuing to follow public health advice, and urge you to continue doing so," said Dr. Eileen de Villa during a COVID-19 update at City Hall on Wednesday.

"These steps for self-protection are as important as ever as we continue to see concerning growth in cases with variants of concern, which spread more easily and cause more severe illness."

Dr. de Villa isn't the only public health official sounding the alarm over these viral variants.

New modelling data released yesterday by Ontario's COVID-19 Science Table shows that, while there has been an overall decline in community spread, the majority of provincial public health units are now seeing an increase in COVID-19 numbers as restrictions are lifted.

"Variants of concern continue to spread across Ontario. Our ability to control the rate of spread will determine whether we return to normal or face a third wave of infection," reads a document released by the table on Thursday.

"We know what works: continued masking and distancing are essential to controlling variants of concern. Our behaviour over the next few weeks is critical in determining the quality of our summer."

COVID update 1/7: New variants are creating a new pandemic (look at the red chart) #COVID19Ontario https://t.co/NcCK6nQO8I pic.twitter.com/j4BWpPArAN

— COVIDScienceOntario (@COVIDSciOntario) March 11, 2021

As of Thursday, Ontario had logged a total of 313,520 COVID-19 cases (an increase of 1,092 over the day previous) with 295,128 considered resolved. A total of 7,109 people have died across the province since the pandemic first hit last winter.

In Toronto, specifically, 101,242 people have tested positive for the coronavirus and 2,704 deaths have been reported.

The city continues to see case counts jump by the hundreds each day, with 397 new cases confirmed between March 9 and March 10 alone. Dr. de Villa announced on Wednesday that 2,327 of the total cases in Toronto had screened positive for mutations of the virus to date.

"The majority of confirmed variants continue to be the highly infectious B.1.1.7 variant, also known as the U.K. variant," she explained to reporters. "There remains a real risk that we will begin to see an increase in COVID-19 cases over the coming days and weeks."

Like federal and provincial authorities, de Villa stressed that the best way to prevent an increase in cases is for everyone to stay at home whenever possible and to continue following current public health guidelines.

"We continue to ask you to stay home and, when you leave the house, to wear a mask and to practice physical distancing," she said.

"This will help us combat the increases we're seeing in variants of concern, and will help us to protect those who are not yet vaccinated."

Today's summary of #COVID19 cases in Toronto: as of March 10 at 2 p.m., there have been 101,242 cases (397 new since March 9), 278 people are in hospital (21 new), 2,703 deaths (4 new) & 94,502 people have recovered (344 new). More info: https://t.co/sxE48Dsyr7 pic.twitter.com/P3N3MhdfOQ

— Toronto Public Health (@TOPublicHealth) March 11, 2021

According to the modelling data released by the province's science table yesterday, Ontario could see upwards of 8,000 new COVID-19 cases per day by April.

That, of course, would be the worst-case scenario. Under a best-case scenario, we could see fewer than 2,000 new cases per day, but it all depends on how we deal with the spread of variants while awaiting widespread vaccinations.

"Our actions now affect our ability to access care later," said the table. "Controlling cases, increasing vaccinations where they will have the greatest impact, and accelerating vaccinations overall are how we beat the pandemic."

Fortunately, vaccination clinics are up and running in Toronto for priority groups such as seniors aged 80 and over. As of Friday morning, the city reports that 226,130 COVID-19 vaccine doses have been administered in Toronto to date.

"As vaccine supply for the general population becomes widely available from the Government of Canada and the Ontario Government, more than 350 clinics, including pharmacies and mobile clinics across Toronto, will vaccinate people based on the priority framework established by the Province," notes the City of Toronto.

"The City of Toronto, Toronto Public Health, hospitals and community healthcare centres are all working together to get Torontonians vaccinated as quickly as possible."

Until then, municipal officials ask that all residents "stay home as much as possible" to stop the spread of new variants and save vulnerable lives.