A story written in water

Results from wastewater sampling in southwestern Ontario show successive versions of the Omicron variant of COVID-19 sweeping through the population between 2021 and 2024. The chart is based on 7,734 individual samples grouped in 14-day intervals. To assemble this picture, researchers tracked more than 120 separate mutations in the genome of the virus. Certain combinations of mutations are the mark of a specific variant. Now that relatively few individual cases of COVID-19 are tested and even fewer genetically sequenced, wastewater offers the most comprehensive picture available of the current state of the virus.

Average frequencies of different COVID-19 variants over time
Oct. 15, 2021 to May 17, 2024

THE GLOBE AND MAIL Source: Art Poon; samples collected by Western University, University of Guelph, University of Waterloo.