STRATFORD -- Public health officials in Stratford are dealing with their worst COVID-19 outbreak since the start of the COVID-19 pandemic.

Three residents at Cedarcroft Retirement Home have died from the disease in less than a week and the number of the cases doubled overnight.

There have been a total of 46 cases at the home, including 34 in residents and 12 in staff. Three people have died.

"It is the largest outbreak that we've had," said Dr. Miriam Klassen, medical officer of health for Huron-Perth Public Health. "Our priority has been to do the case and contact management."

Officials also said there are staffing issues and they're still trying to determine how the virus got into the building.

"We have not determined how COVID was introduced into the facility in the first place," Dr. Klassen said.

Stratford Mayor Dan Mathieson expressed condolences and support for Cedarcroft.

"It is a challenge for family members who have family members who are in the residence and their inability to go visit and check in on them," he said. "For a lot of people it weighs heavy."

All Seniors Care runs Cedarcroft. In an emailed statement to CTV News, company officials said it will take a "great team effort" to get through the outbreak.

"Our staff are determined; they have added shifts when asked, stayed a little longer to make sure all residents have been taken care of, and supported each other throughout each day," the statement said in part. "But that is only part of the team, we have welcomed the support of many important team members from the community including Ontario Health partners such as the Huron Perth Healthcare Alliance with the Southwest Local Health Integration Network and our friends at the Perth County Paramedic Services."

Officials said the team is supporting residents and staff through regular family communication, personal protective equipment, restricting access to essential visitors and self-isolating residents.

"We will continue with our stringent cleaning and disinfecting practices throughout the home and to be at the ready to help support wherever we are needed," the statement said. "By following the safeguards in place, remaining calm and focussing on resident care we will get through this together. Cedarcroft Place is a continuum of care community home to independent living residents."

Huron-Perth Public Health is reporting 48 active cases of COVID-19. The region is currently listed in the province's green tier, but officials acknowledged that recent deaths and cases may move the region into the yellow zone.