The poop doesn't lie — at least in Lynden, where it has helped guide the city's pandemic response for over a year.
The Whatcom city has become home to one of the most thorough COVID-19 wastewater testing programs in the U.S., said Kent Oostra, owner of Ferndale-based Exact Scientific Services. His lab has tested Lynden's sewage for traces of the virus shed in people's feces since June 2020. This data can help predict when a COVID-19 outbreak may be on the horizon, he explained, giving about 10 days of notice before one occurs.
"They've got the tsunami alert 10 second before it comes. This is similar," said Lynden Chamber of Commerce Executive Director Gary Vis. "It's just a heads up. This is here, it's happening."
The sewage testing has proven useful over the last year and a half, Vis said: It's guided the city's community outreach, alerting them as to when they should encourage residents to take more COVID-19 precautions. It's served as an educational tool for those who may be skeptical that infection is actually a widespread issue in Lynden.
And it's helped the city understand whether large gatherings, like the Northwest Lighted Christmas Parade and Northwest Washington Fair, were the root cause of COVID-19 outbreaks.
The testing itself and how it is analyzed has also been refined in this timeframe, Oostra said. His lab has improved its ability to extract the virus from sewage samples and beefed up its understanding of how the data correlates to hospitalization and case rates.
What's so great about poop?
Unlike COVID-19 case numbers tracked by local health departments, sewage samples reflect the infection status of everyone who uses the city's sewage system. This has become particularly valuable as the pandemic drags on, Oostra said, since some people may have lost the motivation to get tested when they have symptoms. At-home COVID-19 tests, whose results aren't factored into official case counts, have become more prevalent as well.
Plus, now that vaccines are available, there are likely more asymptomatic people out there who never get tested because they don't realize they are sick but are still spreading the virus, Oostra said. (About 52% of Lynden's population has initiated vaccination, according to the Whatcom County Health Department.)
"With vaccinations, you now have more asymptomatic people not getting tested," Oostra said. "So cases may not be a number we want to hang our hat on anymore."
Oostra calls sewage data "a true snapshot" of infection in the community, and the current picture it shows isn't so pretty: The amount of virus found in the wastewater sample taken on Sunday, Sept. 26, substantially increased from recent samples and was the third-highest amount detected since Lynden began testing in June 2020, according to a Sept. 28, 2021, Facebook post by the Lynden Chamber of Commerce.
"In other words, this is serious," read the post. It urged community members to get tested and take precautions, like masking and staying home if they have any symptoms.
A successful track record
In January, the importance of wastewater testing became abundantly clear, Vis said.
Communities nationwide saw spikes in new reported cases, according to data tracked by The New York Times. In Lynden, high amounts of COVID-19 detected in the sewage in early January alerted the city that the virus was lurking in the community, prompting leaders to get out in front of the outbreak and conduct outreach.
"We will publish this graph weekly so you can follow the trend for yourself," read a Jan. 13 Facebook post by the Lynden Chamber of Commerce. "Armed with this information, you can decide what you are or are not willing to do."
Within two weeks of the outreach, the number of positive COVID-19 cases began to drop, Vis said.
As large community gatherings became possible again this summer, the sewage testing also allowed city leaders to determine if these events were the root cause behind COVID-19 outbreaks or if infection had begun to permeate the community beforehand. Vis points to the Northwest Washington Fair, which took place in Lynden in mid-August, as an example. He said the amount of COVID-19 in the city's sewage was already creeping up before the 10-day event began.
"When you start reviewing that data longterm, it's like 'Oh, we saw this before the fair,'" Vis said. "So the fair wasn't the cause, the cause was before."
The city tests three wastewater samples a week, at $250 a pop. That comes out to a monthly bill of $3,000 for the service. The program was initially funded with federal COVID-19 relief funds, but the city is now supporting the effort with its own money.
"We felt it was predictive and that the community responded appropriately and took corrective measures to ensure public health," said Lynden Mayor Scott Korthuis.
The Whatcom County Health Department has not made as much use of the wastewater data, according to communications specialist Melissa Morin.
"Wastewater surveillance may indicate how much virus is being shed, but it does not directly help with the Health Department's efforts to limit the spread of COVID-19 through case investigation and contact tracing," Morin wrote in an email to The Bellingham Herald.
Better science, new variants
Testing poop for COVID-19 sounds strange, but testing wastewater for viruses and drugs is actually a decades-old technology, Oostra said. It's been used in other countries to track the virus that causes polio, a debilitating disease.
Oostra's company extracts the virus from wastewater using a high-speed centrifuge, which is a device that spins and separates out the virus particles from the rest of the sample. Compared to other labs doing this testing, Oostra said that his has a more "robust" method of extracting the virus from the sewage samples.
"I'm not throwing darts, I promise you that," Oostra said. "It's science. They are using it worldwide."
His team spent weeks in June 2020 establishing a baseline amount of virus for analyses, so they know when a result is significantly high as opposed to the normal COVID background numbers expected during a pandemic. His team monitors environmental factors that could influence the data as well, such as sample dilution caused by heavy rain.
When the delta variant became the dominant form of COVID-19 in the U.S. earlier this summer, Oostra wondered whether that should change the baseline his team was using to evaluate infection trends. Did the new variant shed more virus particles compared to previous ones? If it did, would that make it seem like there are more people infected in the community even if there aren't?
So far, Oostra hasn't changed the baseline, but he has his reasons. While there have been higher levels of the virus detected in Lynden's sewage recently, there have also been more hospitalizations, he said. Hospitalization rates in Lynden spiked in early September, according to the Whatcom County Health Department. That proves to Oostra that the higher amount of virus in the sewage is correlated at least in part to more people getting sick, not just higher amounts of the delta variant being shed by each infected individual.
"If the shed rate is different, it's not different enough to significantly impact how we evaluate the number we are producing from sewage," Oostra said.
Exact Scientific Services is collaborating with University of Washington virologist Scott Meschke on a report outlining Lynden's testing program and examining whether it did indeed accurately predict when outbreaks occur. The first draft will be finalized in the next two weeks, Oostra predicts.
There have been major advances in wastewater-based epidemiology since the SARS virus spread around the world in the early 2000s, Meschke said. But there is still much to be learned about how the technology can be used to monitor public health, and Lynden is a good location to test these applications due to its manageable population size, he explained.
There has been wastewater testing in Seattle since the early days of the pandemic, but it is more difficult to track COVID-19 there since the city's population is much larger than Lynden's, Meschke said.
"There was always somebody sick in Seattle, but the amount of people not sick dilute out the signal. It was harder to see clear trends," he said. "Lynden is a case where we can actually see there are trends aligning with what the caseload looks like."
What's next in the world of wastewater virus testing? Figuring out how to sequence and identify different variants in the sewage samples, Meschke said. That will allow municipalities to understand how variants are spreading without determining which version every infected person has.
"The delta variant created new trends in the pandemic that we didn't expect," Meschke said. "We expected with vaccines that we would get a drop in cases. But with delta, we got a surge that put us right back where we were when the pandemic started."
