Unless something has changed, I believe an outbreak is declared even if it's only 1 single person who has tested positive. They can't be certain whether or not it has spread, so they declare an outbreak either way. I know for sure this is how LTC homes have been handling it because they can't tell if that 1 person spread it to others.
Edit: Waterloo Region may be moving to Grey as soon as Monday. Dr. Wang is asking the public to prepare for an announcement tomorrow: https://www.cbc.ca/news/canada/kitchener...-1.5845422
Edit: Waterloo Region may be moving to Grey as soon as Monday. Dr. Wang is asking the public to prepare for an announcement tomorrow: https://www.cbc.ca/news/canada/kitchener...-1.5845422