City-wide built environment SARS-CoV-2 detection for COVID-19 surveillance

Area of Science:

• Environmental microbiology
• Epidemiology
• Public health surveillance

Background:

• Built environment surveillance for SARS-CoV-2 (the virus causing COVID-19) shows promise for localized monitoring.
• Its effectiveness for broader geographic areas and populations remains largely unexamined.

Purpose of the Study:

• To evaluate the utility of built environment detection of SARS-CoV-2 for COVID-19 surveillance across wide geographies and populations.
• To assess the relationship between SARS-CoV-2 detected on floors and the overall COVID-19 burden.

Main Methods:

• A prospective city-wide sampling study in Ottawa, Canada (Oct 2022-Mar 2023).
• Weekly collection of floor swabs from public spaces (schools, libraries, emergency departments) for SARS-CoV-2 detection and quantification via RT-PCR.
• Comparison of environmental SARS-CoV-2 data with regional wastewater signals and hospital COVID-19 patient census.

Main Results:

• Over 1,800 floor samples were collected, with 45% testing positive for SARS-CoV-2.
• A strong correlation was observed between SARS-CoV-2 viral load on floors and the hospital COVID-19 patient census (Spearman's r=0.64, p=0.0017).
• Hospital-specific swab viral load strongly correlated with hospital-specific COVID-19 census (Spearman's r=0.76, p<0.0001), while wastewater data showed no significant correlation.

Conclusions:

• Built environment surveillance, particularly from hospital settings, is a strong indicator of infectious disease burden.
• Floor sampling of SARS-CoV-2 provides a more delineated measure of COVID-19 cases within institutions compared to regional wastewater surveillance.
• Findings support the use of built environment surveillance for quantifying infectious disease burden in institutionalized populations.