This is a summary, written by members of the CITF Secretariat, of:
Hegazy N, Cowan A, D’Aoust PM, Mercier É, Towhid ST, Jia JJ, Wan S, Zhang Z, Kabir MP, Fang W, Graber TE, MacKenzie AE, Guilherme S, Delatolla R. Understanding the dynamic relation between wastewater SARS-CoV-2 signal and clinical metrics throughout the pandemic. Sci Total Environ. 2022 Dec 20;853:158458. doi: 10.1016/j.scitotenv.2022.158458.
The results and/or conclusions contained in the research do not necessarily reflect the views of all CITF members.
A CITF-funded study, published in Science of the Total Environment, demonstrated that wastewater-based surveillance (WBS) for SARS-CoV-2 could indicate disease incidence and predict disease burden at various stages of the pandemic. Additionally, during future potential seasonal vaccination campaigns against SARS-CoV-2 and emerging variants, WBS is expected to be able to provide a moderate indication of COVID-19 disease incidence and a strong indication of disease burden in the community. This study was led by Dr. Robert Delatolla (University of Ottawa) with CITF funding directed towards Dr. Sharon Strauss (University of Toronto).
- Prior to global mass immunization campaigns and during the spread of the wildtype SARS-CoV-2 strain and the Alpha variant of concern (VOC), viral measurement of SARS-CoV-2 in wastewater was a leading indicator for both COVID-19 incidenceNumber of newly diagnosed cases and disease burdenImpact of a health problem measured by indicators such as financial costs, new hospital admissions, ICU admissions and deaths in communities.
- As the two-dose vaccination rates escalated during the spread of the Delta VOC from July 2021 through December 2021, the correlation between wastewater signals and community COVID-19 disease incidence weakened. But there was still a strong correlation between WBS and clinical metrics indicative of disease burden (new hospital admissions, ICU admissions, and deaths).
- With the onset of the Omicron BA.1 VOC in December 2021 through March 2022, wastewater again became a strong indicator of both disease incidence and burden: people had less infection-acquired immunity from a recent infection, Omicron was escaping vaccine-induced immunity, and vaccine effectiveness was waning.
- With people gaining more infection-acquired and vaccine-induced immunity shortly before the onset of the Omicron BA.2 VOC in mid-March 2022, wastewater was shown to be a strong indicator for both disease incidence and burden.
- Looking forward, WBS is expected to show moderate indication of incidence and a strong indication of disease burden in communities during future potential seasonal vaccination campaigns.
Wastewater-based surveillance has proven to be a reliable and complementary tool for population-based monitoring of disease incidence. Now, it is evident that the hospitalization-to-wastewater ratio can be a good indicator of VOC virulence when widespread clinical testing is limited. Overall, wastewater-based surveillance can provide information useful to public health decision makers on both infection incidence and disease burden.