Evidence of COVID-19 can be found in an infected person’s feces, so researchers at the University of Minnesota Medical School’s Duluth campus are testing samples of sewage collected at wastewater treatment around the state.

Medical school assistant professors Glenn Simmons Jr. and Richard Melvin are testing samples of wastewater submitted by Minnesota treatment plants — including the Western Lake Superior Sanitary District in Duluth, which treats sewage for more than 125,000 residents — to better understand where COVID-19 is and, eventually, how many people in a certain population have it.

“It’s after several months of doing this and then conferring the data that we have with the data from the Department of Health and other officials, where we may be able to start developing a formula that can help us make sense of it and then help redirect medical resources and public services,” Simmons said.