WINDSOR, ONT. -- The Windsor-Essex County Health Unit says 20 COVID-19 cases are linked to a new cluster in the region.

Medical officer of health Dr. Wajid Ahmed says the first symptom onset date was Sept. 5.

“We have reached out to almost everyone we have identified as close contacts,” says Ahmed.

He says most of the people are in the age group of 20 to 29 years old.

The health unit says it started with a family gathering in Collingwood in early September, then they went to a family gathering in Windsor and subsequent events.Other locations included restaurants, card game and a cottage in Tobermory.

Seventeen cases are still being followed by the health unit and three cases have been discharged.

“The majority of the residents are living in the city of Windsor,” adds Ahmed.

Ahmed says he hopes there will be no further cases related to the cluster.

“They are all linked at this time to family and friends and limited to that setting,” says Ahmed.

WECHU says the cases are all treated as symptomatic.

"Even when we are talking about someone who has a high-risk exposure and some people may argue whether they are false positive or true positive," says Ahmed. "The diagnostic technique that we have, that means they are positive and secondly we have a reason to believe that they had a high-risk exposure and that's why they're positive."

High risk contacts must self-isolate for 14 days to prevent any further transmission. The health unit warns that parties and social gatherings could lead to a large number of cases very quickly.

“If physical distancing and appropriate measures are not taken it could lead to a large number of cases very quickly,” says Ahmed. “It could be a challenge not only to the people who attended that cluster or that event, but also for the rest of the community.”