Wastewater Testing Helps W&L Track Virus Testing sewage samples for the virus that causes COVID-19 is helping W&L to do targeted human testing and identify asymptomatic cases before they trigger large outbreaks.
On Monday and Tuesday of each week, Biology Professor and Department Head Bill Hamilton has an unenviable task on his to-do list. Several times during those 48 hours, he makes rounds on the Washington and Lee University campus, reaching inside manholes to collect sewage samples. The job is as important as it is unpleasant because wastewater testing can alert officials to COVID-19 cases on campus even before clinical symptoms appear.
Since Hamilton began sending samples for testing at the start of Fall Term, two separate positive results have led to follow-up testing that identified asymptomatic COVID-19 cases within the student population. The university was able to quickly quarantine those students and their close contacts, which may have prevented large outbreaks on campus.
“Wastewater testing is a high-resolution surveillance method,” Hamilton said, “because if the virus is detected in a sample, then we know there is somebody shedding it in their waste.”
Wastewater testing is by no means a new practice in the world of infectious disease control, but it is gaining traction at colleges and universities around the world as leaders look to mitigate the spread of SARS-CoV-2, the virus that causes COVID-19. Mami Taniuchi, an associate professor of infectious diseases at the University of Virginia, receives and analyzes W&L’s samples in her clinical laboratory there. When she isn’t in Charlottesville, Taniuchi is often studying the use of environmental surveillance like sewage testing to track disease outbreaks in low- to middle-income countries. For the past 12 years, she has spent about half of each year in Bangladesh, where she works at the International Center for Diarrheal Disease Research.
The Virginia Department of Health put Hamilton in touch with Taniuchi, who is also working with Virginia Tech and Radford University, as well as some Virginia municipalities, to test wastewater samples for SARS-CoV-2. She said wastewater testing alone is not enough, but it is a cost-effective and relatively unobtrusive way to determine where more targeted resources should be deployed. Like other universities, W&L has access to a limited number of COVID-19 tests each week, so the sewage testing is helping to determine the most effective way to use those tests.
“If you are not recovering SARS-CoV-2 from [sewage samples in] a particular building, then I would not go in that building and spend a ton of money to test everyone,” she said. “This is a way to prioritize.”
Hamilton takes a wastewater sample using a cup affixed to the end of a long pole.Hamilton began following research on sewage sampling early in the pandemic, and he began making regular collections on the W&L campus when Fall Term classes began in late August. His rounds take him to five different sites on campus, where he uses a long pole to reach inside and grab samples from the effluvium flowing inside. All of the samples come from on-campus residential buildings where the virus is most likely to be present.
Those samples are hand delivered to Taniuchi’s lab, where they are tested in a process that involves using skimmed milk particles. W&L receives the results within about 48 hours. This test can reveal not only whether SARS-CoV-2 is present in a sample, but how much viral load is in the affected building. If the virus signal increases from one sample to the next, that could indicate an increase in the virus.
One piece of information that cannot be determined by the assay is whether the detected virus is from a contagious or recovered individual. Those who have recovered from the illness continue to shed virus for many weeks after recovering from COVID-19. Early in the wastewater testing experiment, one of Washington and Lee’s samples came back positive, but follow-up tests were all negative. Since several students living in that residence hall had recovered from COVID-19 before arriving on campus, they may have been the source of the positive result.
Another factor that prevents sewage testing from being a catch-all solution at W&L is the fact that it is not possible to include every student in the sample pools. Samples cannot be collected at off-campus locations such as fraternity houses, for example, because they would be mixed with sewage from elsewhere in the city. And in the case of one-half of Gaines Hall dormitory, samples would be mixed with wastewater from the university’s quarantine and isolation center, so a positive result on those samples would not be instructive.
W&L has purchased a piece of equipment called a composite sampler that will allow Hamilton to add two sites to his rounds each week. A composite sampler can be lowered into a manhole and left to collect samples over the course of twelve hours. That will come in handy at the School of Law, which doesn’t generate enough wastewater to do grab testing, and Sorority Row, where the wastewater is too far below the street to be safely collected using standard equipment. The sampler will be useful even after the pandemic because biology and environmental studies professors and students can use it for stream sampling, Hamilton said.
Although wastewater testing is no magic bullet, W&L’s COVID-19 response team expects that it will continue to be a worthwhile tool to have in the university’s prevention toolkit.
“It gives us a heightened awareness,” Hamilton said, “particularly in an asymptomatic population.”
For the most up-to-date information about Washington and Lee University’s COVID-19 response, including the most recent case numbers, visit https://my.wlu.edu/covid-19-resources.