Declining COVID-19 rates in Windsor-Essex sewage suggest spread is slowing

Sewage samples in Windsor-Essex show declining rates of COVID-19, which indicates that cases may soon start to stabilize or decline in the community. 

Since the summer, scientists at the Great Lakes Institute for Environmental Research (GLIER) at the University of Windsor have been taking weekly samples from four wastewater treatment plants: two in the City of Windsor, and one each in the towns of Lakeshore and Amherstburg.

The method is said to indicate the number of cases that will arise in a community as people tend to shed the virus from their body days before symptoms appear. 

When GLIER first started looking at the samples in the summer, COVID-19 cases had slowed in Windsor-Essex. But by the time the second wave came around, the institute's executive director, Mike McKay, said they saw that reflected in the wastewater samples. 

"We had this sort of quiet summer- fall period. We were able to detect the genetic signature of the virus in wastewater in many of our communities ... but certainly as we saw this resurgence, this second wave occur in Windsor-Essex we started seeing this virus spiking coincident with the confirmed cases in the community," McKay told CBC Radio's Windsor Morning host Tony Doucette Monday.  

At first, McKay said they were taking samples once a week from the treatment plants, but in November they increased their frequency to taking samples three times a week. 

And while the results are promising, he said there is limitations to the data.

LISTEN: GLIER head Mike McKay speaks about COVID-19 rates on Windsor Morning 

The signal of the virus in the samples could be diluted from snow melt and other products tossed down the drain, McKay said. 

For this reason, when medical officer of health for Windsor-Essex talked about the data during Friday's COVID-19 briefing he was optimistic but still cautious about what the data means. 

"Again that doesn't mean that things are better, that we are out of the woods, we are not, we still have a significant amount of cases in the community," said medical officer of health for Windsor-Essex Dr. Wajid Ahmed. "Maybe we have hit our plateau and we should start to see some improvement going forward from this point." 

McKay said the purpose of this research was to help public health predict what's to come and that he's "optimistic that maybe this means that some of the mitigation measures that are being taken, adopted in WE, throughout the province might be working."