BARRIE -- The Simcoe Muskoka District Health Unit (SMDHU) announced 21 COVID-19 cases today, seven more than yesterday, signifying the largest one-day spike to date in the region.

SMDHU Medical Officer of Health Dr. Charles Gardner says the numbers are just the tipping point.

"We have an incomplete picture of the people that are affected. For sure, there are people in the community who are infected that we don't know about."

The health unit reports a man in his 40s and woman in her 50s are in hospital, and more cases are under investigation, including Muskoka's first confirmed case.

"This is evidence that it is transmitting in our community, and we've also had a substantial number of people that have been severely affected by this," Dr. Gardner says.

SMDHU's top doc is urging residents to avoid unnecessary travel to and from home, public places and work within the region to cut down on the chances of spreading the virus further.

"We may find that more has to be done that the government moves - the province moves on - even further closures and restrictions on our daily movements."

Today, Ontario reported 100 more COVID-19 cases, bringing the provincial total to 688.

It marks the highest single-day spike for the province.

The increase in new cases at this time isn't unexpected, as many Canadians return home from their March Break travels.

The backlog of people waiting for test results remains over 10,000 in the province.

The majority of those infected are in self-isolation at home.

With files from CTV's Kim Phillips.