What can our wastewater tell us about COVID-19 outbreaks?

Clinically diagnosed COVID-19 cases are only the tip of the iceberg. A significant obstacle in COVID-19 surveillance is the large proportion of infections that go undiagnosed either because individuals are asymptomatic or not tested. Meanwhile, estimates of COVID-19 prevalence are based on the number of clinically diagnosed cases, limiting the success of health care initiatives to prevent the spread of the SARS-CoV-2 virus. This calls for an urgent need for rapid diagnostic tools to detect the presence of SARS-CoV-2 in communities.

Show me your poop and I will tell you how you are doing. We all go to the bathroom and using this central principle, municipal wastewater represents a snapshot of the health status of a community. Such an approach has already been used to provide early warnings of Hepatitis A and Polio outbreaks. Now, we are seeing unprecedented levels of national and international efforts to use wastewater-based testing for early warning of COVID-19 outbreaks.

SARS-CoV-2 can shed through stool, and potentially urine, and has been detected in municipal wastewater. Preliminary studies have shown that the concentration of SARS-CoV-2 found in the wastewater of cities correlates with the number of COVID-19 cases, and more importantly, detection can serve as an early warning mechanism for a potential outbreak. In addition, wastewater testing brings an community-wide assessment of the SARS-CoV-2 circulation in populations, as it detects both symptomatic and asymptomatic infections. Thus, wastewater-based testing can improve, and even accelerate, early detection of SARS-CoV-2 in communities. Combined with clinical and public health data, wastewater-beased testing can be a tool for communities to control the spread of viral outbreaks and provide effective communication to citizens.

Science to the service of the community. To leverage wastewater testing for our community, we teamed up across several UI departments, and brought together experts in microbiology, civil and environmental engineering, and mathematical modeling. Specifically, those involved are the Eva Top lab (including Dr. Erin Mack and myself), Erik Coats lab (including Cindi Brinkman) and Ben Ridenhour Lab (including Dr. Tyler Meadows). This collaborative initiative led the way to establish a method to detect SARS-CoV-2 in local wastewater and develop a surveillance network. We now monitor biweekly the presence of SARS-CoV-2 in wastewater from the city of Moscow, ID as well as the University of Idaho campus. Once our team receives the samples, the viral fraction is concentrated and the virus is inactivated. Then we extract the virus RNA, convert the RNA into cDNA, and detect genes that are specific to SARS-CoV-2 using polymerase chain reaction. This last step is very similar to the clinical diagnostic test.

Trends are the Key! We are have been monitoring the concentration of the SARS-CoV-2 in UI campus wastewater since early September. This way, we were able to detect spikes in viral titers in the wastewater from several University housing areas. The first spikes we detected triggered follow-up clinical testing of students in two residence halls and identified six new positive cases. Now, using a combination of wastewater surveillance and individual testing performed by University’s COVID-19 taskforce, hotspots of infections can be identified and addressed to aid in curtailing the spread of the virus.

As we move forward with our efforts, we are continuously improving our approach. In the near future, we hope to develop mathematical models integrating wastewater surveillance that can predict and forecast outbreaks in rural communities.

To view a recent colloquium on this topic: https://www.youtube.com/watch?v=wzTqw-Trvro