Wastewater testing for the virus that causes COVID-19 reveals a mixed picture of the way the disease may have been circulating in Winnipeg earlier in March. The Public Health Agency of Canada analyzes samples of Winnipeg wasterwater near the city's three sewage treatment plants. The federal agency determines the relative volume of the virus SARS-CoV-2, which causes COVID-19, and also tests the virus to see which virus variants are dominant.