During the city's COVID-19 briefing, Dr. Eileen de Villa warned that Toronto could see more infections in the next few weeks than it did during the peak of the first wave.
Without stricter restrictions to curb the spread of the virus, de Villa said things could get "much worse" this winter.
The doctor said that Torontonians aren't "passive observers" and do not need to wait to protect themselves and others around them.
"Your actions – the choices you make – play a significant part in arresting and even reversing the spread of COVID-19," de Villa said.
"The virus will find it a lot harder to spread if you aren't doing things that help it spread. That's why it is vital to think of your plans as a choice between things you need to do and things you want to do."
For those who live alone, de Villa urges them to connect with others virtually.
Some people with serious mental health needs who need to connect in person with risks, de Villa advises them to meet outside, keep a distance of at least six feet, and wear a mask.
"Believe me, I know – I really do know – that this is a huge ask. No one wants to imagine the worst could happen as a result of a family holiday. But I imagine many of the people in Toronto thought something similar before they began the frightening, and sometimes harrowing experience of battling this illness," she said.
On Wednesday, Toronto Public Health reported 187 new infections, bringing the city's total to 21,315. Of those cases, 1,308 have died while 17,700 have recovered.