SARS-CoV-2 Detection in Wastewater using Droplet Digital PCR by Carol Wilusz, Ph.D.

Before the COVID-19 pandemic, what was your primary role or field of research?

In terms of research, I was studying RNA biology in stem cells and in various diseases such as muscular dystrophy. I also run the Molecular Quantification Core, which is where Colorado State University houses its QX200 ddPCR Reader, and I direct the Cell & Molecular Biology Graduate Program.

How severely has your region been impacted by the pandemic?

Compared to the rest of the country, CSU has seen few cases. As of the end of September 2020, Larimer County, CO., has seen 2,560 cases, or about 717 per 100,000 residents.

How did this wastewater project come about? Who seeded the idea and when?

The Fort Collins Water Treatment Facility first expressed interest in partnering with CSU in May. They connected with me and Dr. Susan DeLong at the Department of Civil and Environmental Engineering. This effort expanded to include the Metro Water Reclamation District, which serves Denver and northern Colorado. We now serve a collaborative involving 18 water treatment facilities and the Colorado Deptment of Public Health and Environment.

Rose Nash, Ph.D., Director of Research and Development at GT Molecular, partnered with us to develop the assay and offers the same tests to other Wastewater Treatment Plants and municipalities. CSU incorporated wastewater testing into its COVID-19 response plan in May and supported the development of the assays.

What was the primary goal? What did you hope to determine or achieve?

One of our goals was to monitor COVID-19 levels in wastewater treatment facilities that cover 60% of Colorado population. The information we collect can inform public health decisions and prevent hospitals from becoming overwhelmed by slowing the spread of the virus. Our other goal was to detect and respond to COVID-19 infection in dorms. Detecting the virus in a dorm could prompt highly targeted individual testing followed by quarantining and contact tracing, thereby stopping an outbreak before it starts.

What Bio-Rad ddPCR platforms did you use to perform your research?

We used the 1-Step RT-ddPCR Kit, the QX200, manual DG [QX200 AutoDG Droplet Digital PCR System].

Why did you choose to use ddPCR technology to measure SARS-CoV-2?

For us, there were three main benefits. Firstly, ddPCR is more sensitive than qPCR and is more resistant to inhibition – in other words, substances that interfere with qPCR amplification. Another major advantage was that Bio-Rad was willing and able to guarantee ample supply of reagents. And finally, we saw the success of the ddPCR-based wastewater testing protocol supplied by Hampton Roads Sanitation District in Virginia.

What was the scope of the project — for example, how many people were in the wastewater catchment area?

For the CSU project, we were looking at 5,000 students in dorms. For the CDPHE/State Project, it’s hard to say; millions of people, for sure. Each wastewater treatment facility processed wastewater from more than 40,000 people.

What were the key outcomes/findings from your project?

We have been successful in detecting and responding to infections in dorms — After five weeks of classes, CSU is still open.

We have been monitoring 18 water treatment facilities since August 1. Our data has been published to a private dashboard, which aims to provide community health information to the Colorado Department of Public Health and Environment as it makes public health decisions. Additional water treatment facilities in the states will be added to the dashboard through GT Molecular and CSU over time.

How do you think wastewater testing using ddPCR might help stop the spread of SARS-CoV-2 in different communities?

Early detection of infection is essential in small communities such as dorms. We can catch infected individuals and quarantine them before they are able to infect others. The approach can be applied to other shared living facilities such as nursing homes, prisons, and military bases.

In larger communities, such as those served by a water treatment facility, we can detect a rise in the level of infection earlier and make informed decisions regarding the level of social distancing required to maintain status quo, rather than allowing infections to get out of control before implementing a response.