Twice a week, mathematics professor Andrea Bruder squats in the sewage tunnels below South Hall, a mostly freshman dorm at Colorado College. She wears head-to-toe protective gear and holds a plastic ladle in one hand and a to-go coffee cup in the other. Bruder hovers above an opening in a large metal pipe and patiently waits for a student to flush.
That flush will flood the pipes with just enough water to carry human waste down to her ladle, then to her coffee cup and eventually to a lab for processing.
According to an analysis by NPR, Bruder’s small private college in Colorado Springs is one of more than 65 U.S. colleges testing wastewater in an effort to monitor coronavirus spread. And that number is growing.
People who have been infected with SARS-CoV-2, which causes COVID-19, shed virus particles through their feces when they go to the bathroom. Wastewater monitoring provides an early opportunity to catch the virus because it can detect an infection days before respiratory symptoms show up, and even if they never show up at all in the case of asymptomatic individuals.
Across the country, campus outbreaks have shut down in-person classes, led to campus lockdowns, and in some cases sent students home. Communal living and socializing has been a boon to the highly contagious virus, with much of the spread happening in dorms and off-campus housing.
Dorm wastewater offers an ideal testing scenario for colleges: People often poop where they live; researchers know exactly who lives in each dorm, which narrows down who could be infected; and testing wastewater is cheaper than regularly testing students, even when followed up by more targeting screening.
In August, the University of Arizona made news for using wastewater testing to help prevent an outbreak. Wastewater testing alerted administrators to the presence of the coronavirus in a dorm, and follow-up testing found two asymptomatic students. This method has also helped identify positive cases at the University of Virginia, the Rochester Institute of Technology and Colorado State University, which has been running a robust wastewater testing program since the start of the fall semester.
On the CSU campus in Fort Collins, environmental engineering professor Susan De Long stands next to a manhole cover nestled in the landscaping outside Westfall Hall. The dorm is one of 17 sites being tested three times a week across campus.
Students bike and skateboard by as two graduate students — dressed in white protective suits, gloves, masks and hard hats — pry open the manhole cover, exposing the sewer system below.
Unlike Andrea Bruder, De Long and her team don’t have to crawl underground and wait for a flush to collect samples. Instead, there’s a pump that does the dirty work for them, collecting wastewater every 15 minutes over a 24-hour period.
Taking samples over 24 hours allows researchers to catch students who go to the bathroom in the morning and those who go after dinner. “We can’t just assume that everybody is going to the bathroom at 7:30 a.m. or 6:30 p.m., because [students] have different schedules in college,” says De Long, who previously studied pharmaceuticals in wastewater.
When it’s time for the graduate students to fill up their test tubes, they simply lift a big gray tub and pour out a bit of the yellowish fluid.
Abbie Modafferi, one of the graduate students collecting samples, says she avoids smelling the liquid (some samples, she says, are worse than others). But she’s happy to be contributing right now. “I feel like if we’re really trying to slow the pandemic and help get back to normal, the biggest thing is prevention. And this is how you do that.”
Once the samples are pulled from the sewers, they travel across campus to a microbiology lab, where they’re processed. Some colleges outsource this step, but CSU has the space and lab machines to run the analysis in-house.
The wastewater testing can’t tell CSU, or any campus, who is infected with the coronavirus. And because people shed different amounts of the virus at different times during the course of the infection, there’s no way to know how many students might have it.
“We don’t know if it’s 10 people with a little virus or one person with a lot,” says microbiologist Carol Wilusz, who runs the CSU lab.
Instead, the data is used to show trends.
“We’re constantly adjusting our testing protocol based on what the wastewater data is telling us about where we might find the next outbreak beginning,” explains De Long. “When we see a spike at that dorm, we can quickly roll out clinical tests of those students, identify individuals that are infected, and move them to quarantine locations so we can stop the outbreak from becoming larger rapidly. It’s allowed us to stay open, with classes face-to-face.”
Traces of the virus tend to linger in human waste after a person is no longer contagious. CSU makes note of students who have previously tested positive, so when they move back into the dorms, after their isolation, researchers can account for any increased levels connected to their return.
According to Wilusz, CSU’s efforts seem to be working: When they’ve identified elevated levels of the virus in wastewater, follow-up testing has found positive cases.
“I never really believed it was going to work this well,” she says. But she’s grateful it has — not just for her own research, but because her son is a freshman this fall, living in the dorms. “I have an ulterior motive,” she says, laughing. “I’m keeping an eye on that one.”
Wilusz estimates it costs CSU about $25,000 a month to process and analyze the wastewater samples. “It’s a lot cheaper than doing individual clinical tests,” she says, “but it’s not a cheap undertaking.”
Testing wastewater for SARS-CoV-2 is an emerging field. Often colleges are figuring it out on their own, leaning on city utilities or nearby campuses that have their own testing programs. And this type of testing has limitations. For it to be most effective, researchers would ideally be able to take samples from each individual dorm, rather than a cluster, to minimize the number of follow-up tests. But campus sewer systems don’t always make that easy. And a robust on-campus monitoring system only goes so far — many colleges that opened in person saw the virus spread through off-campus parties and housing, away from the dorms that were being monitored.
That’s why Andrea Bruder is optimistic about the program she’s piloting at Colorado College, where most students live on campus. She and her team are still working out the best testing sites, visiting noisy facilities rooms in search of the perfect sewage pipe.
In her 11 years on campus, Bruder had no reason to know about the dorm sewage lines — much of her research focused on ladybugs and aphids on yucca plants. But like so many faculty and staff members at U.S. colleges, she’s redirected her research to focus on COVID-19, using her expertise to keep the campus safe.
With just two testing sites, the operation is still small, and the college hasn’t yet invested in a 24-hour pump, like CSU has. That means Bruder has to fetch the samples herself — and spend her evenings crawling into dark, damp tunnels, waiting for a flush.
It’s still unclear whether testing dorm sewage, followed by focused clinical testing, will work as well as widespread testing of all students. Experts say it’s a tool, to be used with many other tools, including random clinical testing, hand-washing, mask wearing and social distancing.
For now, it’s offering some college communities a drop of hope, courtesy of No. 2.
NPR’s Lauren Migaki contributed to this report.