‘WASTEWATER SURVEILLANCE’ DETECTS VIRUS BEFORE TRADITIONAL METHODS
A week before the Virginia Department of Health reported a spike in coronavirus cases coming from Hampton Roads at the beginning of the summer, the increase was being detected not through nose swabs, but in our pipes and sewers.
Jim Pletl, the water quality director at the Hampton Roads Sanitation District, saw genetic material from the virus surge in the wastewater being produced by hundreds of thousands of Virginians when he analyzed samples from the utility company’s nine plants. As he plotted his data over the health department’s data, he saw similarities, although there was a delay.
“We found the lag time between the time we start to see signals in the wastewater and the time the clinical data starts to change is at least a week,” he said.
The process is called wastewater epidemiology. It’s a way to
detect the virus’s presence pretty soon after people flush the toilet, instead of waiting for them to get tested and get their results back, which can take several days. While SARS-CoV-2 — its official scientific name — is primarily thought of as a respiratory virus, scientists have found that it can affect the digestive system, and the virus’s genetic material has been detected in stool specimens even before people showed symptoms.
Since the beginning of the pandemic in the U.S., Pletl and other scientists have been tracking the coronavirus through millions of gallons of wastewater coming through the pipes around Hampton Roads. And scientists say it could be an early indicator of where the next outbreak could happen.
“Today it’s COVID; we don’t know what kind of pandemics we’ll see in the future,” Pletl said. “Instead of waiting for people to get sick and then have the clinical information, the idea is to use this information to make decisions sooner before things get worse.”
How it works
Each week since March 9, an HRSD water quality specialist has been visiting all nine of the sanitation district’s major plants and collecting about four to six liters of untreated wastewater. Each sample is a composite of the water that has been coming through the plant over the past 24 hours (the virus isn’t thought to be active and infectious once it’s found in fecal matter).
Because the virus isn’t super prominent in the wastewater, the samples have to be taken to the central lab in Virginia Beach and concentrated, with the fecal material and water filtered out using chemicals and a small electronegative filter.
Then, as one scientist described it, all the microbes in the viruses — not just coronavirus, but norovirus and other common viruses found in stool — are “cracked open” to look for genetic material — specifically nucleic acid, a key feature of SARS-CoV-2.
Using technology called quantitative preliminary chain reaction — the same test that’s used to analyze our nose swabs — scientists then look at how many segments of nucleic acid are associated with coronavirus and come up with a measurable figure, “virus per liter of wastewater,” which they analyze over weeks and months, looking at which plants the samples came from and determining where the virus is prominent.
The entire testing process takes about five to six hours.
Filling gaps
The idea of wastewater surveillance is not new. It’s been used to track polio and combat the opioid crisis, and in Hampton Roads, HRSD has been using the same technology to find bacteria indicative of leaking wastewater lines that seeps into area streams and rivers. Now, environmental scientists and health officials in Texas, New York, Ohio and Nevada are among a growing group of people watching how the coronavirus is moving through communities.
Scientists say it’s not enough to rely on testing people, isolating them and tracing their contacts to understand trends, especially with the capacity issues, long testing turnaround times and risks of false negative results still impacting many communities. Wastewater monitoring could complement that process, with environmental engineers working in tandem with health care workers and medical lab technicians.
Beyond being an early indicator of the next outbreak, experts say wastewater epidemiology can also be useful in directing resources like tests, contact tracers and, eventually, treatments to hot spots sooner, especially when those hot spots aren’t being detected through health department data because communities have unreported cases that are missed.
The HRSD scientists have been passing along their findings to the Virginia Department of Health since March, and were told the health department is providing the information to the governor’s office.
A spokeswoman from the health department said in an email they’re not “actively” using the HRSD wastewater data to make decisions “at this point,” but they’ve been forwarding the HRSD wastewater data to local health districts.
“Wastewater surveillance for SARS-CoV-2 is a very young science with no set standards or protocols,” the spokeswoman, Maria Reppas, said. The Centers for Disease Control and Prevention and the Water Research Foundation are among the entities recommending procedures, but since there are various ways the samples can be collected, concentrated and tested, the health department hasn’t adopted wastewater surveillance as a tool yet, Reppas said.
Gov. Ralph Northam has repeatedly said he would use science and data to determine the need for restrictions such as stay-at-home orders and wearing masks.
It’s difficult for the scientists at HRSD to tell how many people are actually infected based on their sampling, because they don’t know how much of the virus’s genetic material people are shedding into their wastewater. They’ve tried estimating with models, but the uncertainty was too great.
“The overall goal here is to look at prevalence,” said Raul Gonzalez, an HRSD environmental specialist who spearheaded the project with Pletl. “You don’t want to make decisions on this data alone.”
Instead, they’ve have been looking at broad trends around the sanitation district’s nine major treatment plants, which collect wastewater across 3,100 square miles. But with the right resources, their COVID-19 surveillance methods could be scaled down to a neighborhood, a prison, or — if they open up again — schools.
“If you tested the wastewater at the schools, you’re probably going to find something,” Pletl said. “Then what are you going to do about it? Close down schools? Or i mplement other safety precautions?”
For now, HRSD’s goal is to capture enough data throughout the year to prove it’s a useful tool to catch future outbreaks before too many people are infected and the information shows up in a clinical database.
“Before we get a vaccine, we’re going to have this long history of data and we’re going to be able to use that data to say, ‘OK, this is what the data can help us with and here are its limitations,’” Pletl said.
Marie Albiges, 757-247-4962, malbiges@dailypress.com