Fascinating Feces: Searching for COVID-19 in community wastewater
Published: Tuesday, February 6, 2024
Most people (other than parents of babies and toddlers) don’t think much about poop, but for epidemiology Professor Katrin Kuhn, poop is her passion. More specifically, analyzing wastewater samples for infectious diseases. Kuhn and her family moved from Denmark to Oklahoma in the middle of the COVID-19 pandemic. When she joined the faculty at the Hudson College of Public Health, she promptly dove into wastewater surveillance for COVID-19. “I was really lucky to find a team here who immediately invited me to be a part of their surveillance,” Kuhn says. In August of 2020, the team began looking for COVID-19 in wastewater from the OU Norman campus dorms. Shortly after, surveillance expanded to include sites in Oklahoma City, Tulsa, and Anadarko. The team currently samples from several locations in Oklahoma City, Tulsa, and Anadarko, including some dynamic sites that they can move around based on where cases are increasing or there is an outbreak of interest.
Kuhn recognizes the benefit of having a cross-disciplinary team that includes engineers, microbiologists, epidemiologists, and community health planners. She notes that the engineers are key in helping to determine the best locations for monitoring sites based on wastewater flow and population. “We don’t want to test in locations with too many factories and big businesses,” Kuhn says. “Those areas have completely different wastewater outputs than residential areas, and we want data (and poop) from where people are living.”
When asked how it works, Kuhn explained that the team uses a little machine with a hose that leads into the sewer system through a manhole. The machine collects sewage samples for 24 hours, and then someone from the team picks up the sample and drives it to the lab on the OU Norman campus. In the lab, the researchers purify the sample, extract the virus RNA [aka the genetic information], and test the sample using PCR analysis. The analysis determines if the virus is present in the sample and, if it is, how much of the virus is present. The team can also test for different variants, which allows them to quickly catch outbreaks from new variants.
You might wonder why someone would want to study poop samples. Kuhn, who has worked in infectious disease surveillance for 15 years, has always been bothered by the fact that it takes so long to get surveillance data. “You are only getting the tip of the iceberg,” she says. “You only get the cases reported where people are ill enough that they go to the doctor, then the doctor has to order a sample, the sample has to be analyzed by a lab, they have to find the virus or bacteria in the sample, and finally the result has to be reported to the health department.” There are so many places in that process where a case could fall out and not be reported.
In many ways, wastewater surveillance is easier (and faster) than traditional surveillance measures. It doesn’t require taking individual samples from people to see what’s going on. “Obviously, I can’t tell whose poop is who's,” quips Kuhn. With wastewater surveillance, researchers capture data from an entire community, including the people who are infected but never go to the doctor or get tested. “It gives us a completely different picture of what the disease burden actually is,” says Kuhn. The hope is that wastewater surveillance will help public health researchers identify outbreaks in rural locations and areas with limited health care where people often don’t, or can’t, get tested by physicians.
When Kuhn and her team find high levels of COVID-19 (or another pathogen) in a sample, they immediately notify the corresponding local county health department. Health department employees can then go into the community and encourage testing, vaccinations, etc. Kuhn also mentioned that, early on when COVID-19 hospitalization rates were high, her team would notify local hospitals so the health care personnel would be prepared for a future influx of patients.
Kuhn sees wastewater testing as the backbone of future disease surveillance, and she hopes that eventually we will have sites in every community across the nation. “It’s a cheap, simple, and fast way to identify diseases in a community,” she says. The team recently signed an agreement with the Oklahoma State Department of Health to develop a statewide wastewater surveillance network. “We will have more than 40 locations that we’ll be monitoring, not only for COVID-19 but also to investigate how we can monitor for other diseases caused by food-borne and vector-borne pathogens,” notes Kuhn. The biggest issue that the team faces is working in rural areas where there isn’t an existing community wastewater system. An example of this is homes with septic tanks. This is something that the team is currently considering as they try to find a way to fit their surveillance into different types of sewage systems.
As an infectious disease epidemiologist, the pandemic proved to be beneficial for Kuhn and her research. “It was a fantastic opportunity for me to be able to set up the wastewater surveillance and learn how we can use this technology in the future with other diseases as well,’ she says. In many ways, Kuhn credits the pandemic with making the idea of wastewater surveillance more palatable to the general public.
When asked why she chose to study public health, Kuhn vividly recalls sitting in a master’s degree course at the London School of Hygiene and Tropical Medicine and hearing a lecture focused on the interplay between climate change and health in developing countries. “I kind of saw the light with that lecture, and I thought maybe this is something I could do with equations and predictions that could help people,” she says. Kuhn appreciates that her students could have a similar epiphany in the graduate courses that she teaches at the Hudson College of Public Health. In fact, several of her students have been involved in the wastewater surveillance research, and most have used their work as a basis for thesis or practicum projects. “The best part of the work I do is to see the students get excited about my research and experiences,” notes Kuhn. “It makes it all worthwhile.”