Measuring SARS-CoV-2 in wastewater solids could help track COVID-19 spread

Scientists have analyzed compounds in wastewater to gauge various aspects of public health, including narcotics usage, antibiotic resistance, and, more recently, the spread of SARS-CoV-2, the novel coronavirus that causes COVID-19.

Now, researchers reporting in ACS' Environmental Science & Technology have discovered that measuring SARS-CoV-2 in settled solids from sewage treatment plants could be a more sensitive approach than measuring the virus in wastewater flowing into the facilities.

SARS-CoV-2 genes have been detected in the feces of many infected people, but it's currently unknown whether the virus particles are intact and capable of infecting others. The flushed genes end up in wastewater, which makes its way to a community sewage treatment plant.

There, solids are removed in settling tanks before the water is further treated and disinfected. Most previous studies have examined the prevalence of SARS-CoV-2 genes in influent, which is the raw wastewater flowing into the plants, but Krista Wiggington, Alexandria Boehm, and colleagues wondered if the virus might be easier to detect in the settled solids.

If so, measuring SARS-CoV-2 levels in wastewater solids could be an effective way to monitor the spread of COVID-19 in communities.

The researchers collected and analyzed influent and settled solids from two sewage treatment plants in California over several days in March and April 2020.

They found that the solids contained 100-1,000 times higher concentrations of SARS-CoV-2 genes than the wastewater influent on a per mass basis, making detection more sensitive and accurate for the solid samples.

Then, the team used methods that they had optimized to analyze settled solids collected from one of the plants almost daily for more than 89 days.

They found that the concentrations of SARS-CoV-2 genes on different days correlated with the number of new cases reported on those days in the community served by the treatment plant. In combination with COVID-19 testing, the approach could help guide public health responses to the pandemic, the researchers say.