Five new COVID-19 cases are confirmed on Tuesday, including a Barrie boy.
The four other new cases include a Barrie woman 18 to 34, a Barrie man 65 to 79, and a man and woman from New Tecumseth, both 18 to 34.
"This is a very substantial increase in our case count," said Simcoe Muskoka District Health Unit's (SMDHU) Chief Medical Officer of Health Dr. Charles Gardner. "We have not had a weekly increase of this magnitude since June 21."
The rise cases across the region comes as students prepare for back to school and child care centres ready to open at full capacity.
According to the SMDHU, the new cases are under investigation to determine how the individuals contracted the virus.
The health unit has declared two institutional outbreaks at Mill Creek Care Centre in Barrie and The Pines Long-Term Care in Bracebridge, both where a single staff member tested positive.
Meanwhile, Ontario is reporting 112 new COVID-19 cases today, and one virus-related death.
Health Minister Christine Elliott says 27 of the province's 34 public health units are reporting five or fewer new cases.
She says 18 health units are reporting no new cases today.
The province was able to complete more than 23-thousand-500 tests over the previous day.