Lydia Cheng


DOI bib
Omicron COVID-19 Case Estimates Based on Previous SARS-CoV-2 Wastewater Load, Regional Municipality of Peel, Ontario, Canada
Lydia Cheng, Hadi A. Dhiyebi, Monali Varia, Kyle Atanas, Nivetha Srikanthan, Samina Hayat, Heather Ikert, Meghan Fuzzen, Carly Sing-Judge, Yash Badlani, Eli Zeeb, Leslie M. Bragg, Robert Delatolla, John P. Giesy, Elaine Gilliland, Mark R. Servos
Emerging Infectious Diseases, Volume 29, Issue 8

We determined correlations between SARS-CoV-2 load in untreated water and COVID-19 cases and patient hospitalizations before the Omicron variant (September 2020-November 2021) at 2 wastewater treatment plants in the Regional Municipality of Peel, Ontario, Canada. Using pre-Omicron correlations, we estimated incident COVID-19 cases during Omicron outbreaks (November 2021-June 2022). The strongest correlation between wastewater SARS-CoV-2 load and COVID-19 cases occurred 1 day after sampling (r = 0.911). The strongest correlation between wastewater load and COVID-19 patient hospitalizations occurred 4 days after sampling (r = 0.819). At the peak of the Omicron BA.2 outbreak in April 2022, reported COVID-19 cases were underestimated 19-fold because of changes in clinical testing. Wastewater data provided information for local decision-making and are a useful component of COVID-19 surveillance systems.