For eight days, Allandale Station Retirement Residence in south-end Barrie was operating under an outbreak declaration after one resident tested positive for COVID-19.
However, two follow-up tests came back negative and the original swabbing was determined to have been a false-positive result.
The outbreak was quickly rescinded.
Dr. Charles Gardner, medical officer of health with the Simcoe Muskoka District Health Unit, said there were several factors that led to the false-positive test.
"The individual, who was asymptomatic, had no direct contact with anyone other than a close contact — who tested negative — in the two weeks prior to the positive result," he said.
The two follow-up tests were negative and there were no other positive cases identified from the universal swabbing of staff and residents at the Yonge Street facility last week, Gardner added.
"Testing of asymptomatic persons, such as this individual, is more likely to yield a false positive than testing of symptomatic persons," he said. "What this means is that when we start testing in populations that aren’t exhibiting symptoms, or who do not have known exposures — so there a lower likelihood of the disease in the base population being tested — we are more likely to experience false positives, given the lower proportion of that population that actually has the disease."
On Friday, May 1, the outbreak was declared at the Yonge Street facility after one resident tested positive for the virus. The Allandale Station outbreak was officially declared over May 9.
