Why feds are pointing out limitations to wastewater tests for COVID-19

A new report from a congressional watchdog agency says more needs to be done to standardize the monitoring of COVID-19 and other diseases through wastewater surveillance, now a key way for Utahns to track the spread of the virus.

“Wastewater surveillance may have enormous potential as a public health tool, but some aspects of science may need further development,” according to the “Science and Tech Spotlight: Wastewater Surveillance” report released earlier this week by the Government Accountability Office.

Testing sewage samples for pathogens, including viruses, drugs and toxic chemicals, can serve as an early warning system to alert authorities of the increased spread of disease, illegal drug use or other public health issues, the report stated.

As an example, the report pointed out low levels of COVID-19 can be detected in human waste “before symptoms appear, as early as one to two weeks before an infected person may seek clinical testing” as well as in those who never experience symptoms , “Who make up about 70 percent of cases and may not seek clinical testing.”

But there are also challenges, the report added, such as privacy concerns over the access to genetic information, issues with animal feces and other potential contaminants, as well as dilution from rainwater washing down storm drains, costs, and particularly, no uniform methods for sample collections, analysis and data sharing.

That lack of standardization “complicates efforts to aggregate, interpret, and compare data across sites and develop large-scale public health interventions,” the report said, noting that some scientists see a benefit to making testing for COVID-19 in wastewater the same nationwide .

Under Utah Gov. Spencer Cox’s new “steady state” plan to treat COVID-19 more like the flu or other deadly diseases with limited outbreaks, the state is focused on wastewater surveillance, along with emergency room visits, to monitor the spread of the virus rather than case counts as fewer reported tests are being done.

Karen Howard, the GAO’s director of science and technology assessment, told the Deseret News that how the public may interpret the wastewater surveillance data was not taken into account in writing the report, “partly” because of its technical nature.

“We thought of it mainly in terms of how public health authorities would use the data that they were gathering rather than how the public might do that,” Howard said, adding wastewater surveillance is “a useful technique that has its purposes but it also has limitations. ”

And the better the public understands the limitations outlined in the report, “the better they can take whatever actions they might want to take based on the results of that sort of communitywide view of pathogen level,” she said.

What’s not clear is how the public should evaluate the data, which in Utah includes a map showing whether the virus has increased, decreased or stayed the same at the sites where testing is being conducted as well as a separate chart indicating risk levels ranging from ” elevated ”to“ watch ”to“ low ”to“ below reporting limit ”to“ insufficient data. ”

“I think it’s difficult to know how the public should interpret it. I’m not sure the public authorities fully have a handle on how they should interpret it, either, ”Howard said. “They’re watching levels of the pathogen go up or go down. They’re judging that from the status of the virus, or from a surge in a community. ”

At this point, the data is probably most useful to indicate how the spread of COVID-19 is trending “rather than a number interpretation method,” she said, but just when the detection of more virus indicates a community may be headed for an outbreak – and what actions the public should then be taking – are not clear, either.

“I do not think we have a lot of experience with that yet as a nation,” Howard said. She said the goal of the report, which is sent to members of Congress and other policymakers, is to focus attention on the need for standardization in wastewater surveillance.

“Once you do standardize, then the next question becomes how do we use the data we’re collecting to make policy decisions,” she said. “And again, I do not think as a public health community, there’s a good handle on that yet, on what these numbers should be telling us and what we should be doing.”

Utah was one of the first states to look for the virus in sewage, starting a pilot project shortly after the pandemic began more than two years ago and now collecting samples twice a week from sites representing some 88% of the state’s population, said Nathan LaCross , the Utah Department of Health’s wastewater surveillance manager.

The Centers for Disease Control and Prevention tracks wastewater surveillance data from more than 750 sites, although few have current data and are scattered over just over a dozen states. The data is not used by the CDC to calculate COVID-19 risks by county to determine when masks or other precautions are recommended.

LaCross has said a new wastewater surveillance website is in the works to better showcase the trends identified through what he called a “statistical process,” acknowledging there’s “not a super-scientific method” to measuring how alarming those trends actually are.

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Maddi Crezee gets a sample of raw sewage at the Salt Lake City Water Reclamation Facility in Salt Lake City on Wednesday, April 6, 2022. The water at the facility is tested for COVID-19 twice a week.

Jeffrey D. Allred, Deseret News

Han Kim, a professor of public health at Westminster College, has described the state’s current reporting on the results of analyzing what Utahns flush down the toilet as frustrating, especially for lay people. Even as an epidemiologist, Kim said it’s hard for him to know from the data available when there’s a true rise in cases.

But Dr. Brandon Webb, an Intermountain Healthcare infectious diseases physician, expressed more confidence in Utah’s wastewater surveillance, calling it helpful. He also said it’s just one of the tools that’s needed to track the virus.

The doctor said the map marking fluctuations in COVID-19 levels at the wastewater treatment sites where samples are collected is the type of information that is especially useful to the public because it is “visibly easy to recognize in terms of geography where we’re starting to see hot spots. ”

But even combined with the “more granular data” that’s more useful to epidemiologists and other professionals, like how many millions of gene copies per person per day are being found, Webb said wastewater surveillance is not the only way to keep an eye on COVID- 19.

“We are still watching other measures,” he said, including test results, hospitalizations and deaths.

That’s the same data that had been reported daily by the Utah Department of Health throughout the pandemic. As of April 1, when the governor’s new pandemic response took effect, the state health department is updating its public dashboard, coronavirus.utah.gov, just once a week.

While that means most Utahns only see new data on Thursdays, Webb said it’s important to recognize that public health officials and other policymakers still have access to the information that’s being collected about the virus on a daily basis.

“Even though the public reporting has scaled back in terms of frequency of updates, I still have a high degree of confidence that our department of health colleagues and our epidemiologists in the department of health are paying close attention to all available epidemiological surveillance data,” he said.

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