Approximately 55 per cent of of the new cases cannot be traced to a clear source, Dr. David Williams said at a news conference Friday afternoon.
"It is still perplexing to me that we're not making major headway going down on that," Williams told reporters. "It makes me wonder if people are being less than consistent in their physical distancing, and if they were in close contact, if they were not wearing a facial covering in those few moments."
"You still have to do that or we're going to be in this plateau for quite a while."
Williams made the comments on a day that saw 477 new confirmed cases of the virus — an uptick in a week where the number of new coronavirus cases appeared to be trending down. Ontario's new case counts fell below 400 on three out of the last four days, with the lowest being 370 on Monday.
Earlier in the day, Premier Doug Ford said the province Ontario needs to increase its daily COVID-19 testing to 20,000 as the province looks toward slowly reopening.
Speaking at his daily briefing, Ford said three things were on his mind when he awoke Friday morning: long-term care, personal protective equipment and Ontario's new job numbers, which he said "weigh heavy on my heart."