Emerging Infectious Diseases (Aug 2023)

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

DOI
https://doi.org/10.3201/eid2908.221580
Journal volume & issue
Vol. 29, no. 8
pp. 1580 – 1588

Abstract

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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.

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