Researchers at the University of Virginia have narrowed down best practices for testing wastewater for COVID-19 in dorms.
A collaboration among UVA Health and the university’s School of Medicine and School of Engineering found wastewater testing methods used in an eight-week study caught 96% of COVID-19 cases across two student dormitory complexes.
The findings included comparisons to periodic COVID-19 testing UVA provided to its students.
Researchers said the testing protocols offer some of the first clear guidance on the most effective methods to perform testing to detect COVID-19 in wastewater.
“We had really been challenged early in the pandemic to detect COVID-19 in the highest risk congregate living settings,” UVA Health’s Dr. Amy Mathers, an infectious disease expert in the medical school’s Pathology Department, told WTOP. “We wanted to detect cases early and effectively.”
The research team led by Mathers and Lisa Colosi-Peterson, an associate professor in the School of Engineering, compared and evaluated sampling and analysis techniques by testing them within buildings with known numbers of positive cases.
Mathers said researchers set up at a maintenance hole next to a building where a pipe would catch all the outgoing wastewater. The waste could be from laundry, a sink or a toilet.
“We drop a tube down and get these programmable robots to pull up water every 15 minutes over a 24-hour period so we have a complete collection,” Mathers said. “We then take a sample and spin it down to the lab and send it for PCR detection.”
Mathers said the team did this six days a week.
“This work could be applied to surveillance in buildings where people live in groups, where transmission may be hard to control but the risk of spread could be high.”
The process allowed the team to determine strengths and limitations of testing wastewater as a tool for monitoring COVID-19 in a building population.
One of the strongest findings, Mathers said, is that the team was able to tell when new outbreaks were occurring.
She said the telltale sign was when tests from the same source would consistently come back negative and then there would be a new positive case.
Another finding concluded that wastewater testing can detect small numbers of asymptomatic cases, something not previously documented.
“Since we can identify new infections with high sensitivity, it provides an early warning signal of when to test everyone in the building to find and isolate the newly-infected persons before an outbreak becomes large.”
However, the ability to detect initial infections was offset by not being able to determine the number of occupants infected or the period of time they had been infected,” Mathers said.
The study found that wastewater detected both active and former cases. But, researchers could not distinguish between new infections from those who had recovered from COVID-19 and were no longer contagious.
“It is very difficult to separate new infections with people who are recently infected, which is one of the limitations of this type of testing that we struggle with,” Mathers said. “The fact that once people are infected they continue to shed nonviable SARS-CoV RNA — that can make the test look positive even though the person may have recovered and is no longer contagious.”
Another finding determined that refrigerated samples “on ice” were adequately preserved for same-day testing, but institutions that planned to send out the samples for testing may need to take additional steps to preserve the samples. Cleansers and disinfectants used in labs could also degrade the viral RNA over time, the study found.
The research concluded that wastewater testing is promising for detecting and controlling COVID-19 in places where people live in close quarters.
“Passive pooled surveillance of wastewater is now serving as an early warning system in many dormitories, barracks and prisons to identify new cases in situations where transmission risk is high,” Mathers said. “Applications for wastewater surveillance to inform and control infectious disease transmission will continue to evolve, but it is hard to believe how far and how fast we have come in the last year.”
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