Lambton Public Health is now breaking down Sarnia-Lambton's COVID-19 cases by region.
A map now appears on the health unit website that identifies where cases have occurred based on three urban and two rural zones.
Medical Officer of Health Dr. Sudit Ranade said each area contains a population of at least 20,000 to protect personal privacy.
The most cases by number and per 100,000 population are in two of the urban zones including central Sarnia and Point Edward and south Sarnia and Aamjiwnaang.
Dr. Ranade told Sue Storr on CHOK (103.9 FM, 1070 AM) Tuesday morning that he cautions against reading too much into the numbers.
"If you get an outbreak in a long-term care home, that's in one area and all of a sudden it's going to look like you have a spike in cases there, that's one example," said Dr. Ranade. "The other piece, too is that you should really look at both sides of that data -- there's cases, but there's also rates. The number of cases is going to correspond generally with just the number of people in that area, so if you have more people you're going to have more cases, just by statistics."
Dr. Ranade said there's a notification in bold above the map that stresses it can't be used to make decisions about your personal risk.
He said there are good reasons for that.
"One, by the time we can tell you about a case, the place where that transmission occurred is long gone, it's one to two weeks ago, so it's really basically telling you someplace you shouldn't have been but already were, or weren't," he said. "The second thing is that it's only based on the places where people live, and so it's not really necessarily based on where they were exposed."
Lambton County Council ordered the more detailed reporting system in September in response to concerns that not enough case information was being made public.
-With files from Sue Storr
(Mapping discussion begins at the 9:30-mark)
https://soundcloud.com/blackburnradio-sarnia/covid-19-lambton-county-medical-officer-of-health-dr-sudit-ranade-oct-20-2020