Why the feds are highlighting the limits of sewage testing for COVID-19

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

“Wastewater surveillance may have enormous potential as a public health tool, but some aspects of the 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 to increased spread of disease, consumption illegal drugs or other public health issues, the report said.

As an example, the report pointed out that 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 can seek clinical testing.” as well as in those who never show symptoms. , “which account for approximately 70% of cases and may not require clinical testing”.

But there are also challenges, the report adds, such as privacy concerns over access to genetic information, problems with animal feces and other potential contaminants, and the dilution of drinking water. rain washing away storm sewers, costs and, in particular, the lack of uniform methods for sampling, analysis and data sharing.

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

Under Utah Governor Spencer Cox’s new “stable state” plan to treat COVID-19 more like the flu or other deadly diseases with limited outbreaks, the state is focusing on monitoring sewage, as well as emergency room visits, to monitor the spread of the virus. rather than the number of cases because fewer reported tests are being carried out.

Karen Howard, GAO’s director of science and technology assessment, told Deseret News that how the public may interpret wastewater monitoring data was not considered when writing the report, ” in part” due to its technical nature.

“We thought about it primarily in terms of how public health authorities would use the data they were collecting rather than how the public might,” Howard said, adding that wastewater monitoring is “ a useful technique which has its objectives but it also has limits.”

And the better the public understands the limitations outlined in the report, “the better they can take the actions they want to take based on the results of this kind of community view of the pathogen level,” she said.

What’s unclear is how the public should assess the data, which in Utah includes a map showing whether the virus has increased, decreased or stayed the same at sites where testing is being done as well as a separate table showing risk levels ranging from ‘high’ to ‘monitor’ to ‘low’ to ‘below reporting limit’ to ‘data deficient’.

“I think it’s hard to know how the public should interpret it. I’m also not sure that the public authorities are entirely clear how they should interpret it,” Howard said. “They watch the levels of the pathogen go up or down. They judge this by the state of the virus or an upsurge in a community. »

At this point, the data is probably most useful for indicating how the spread of COVID-19 is changing “rather than a method of interpreting numbers,” she said, but just as the detection of more Virus outbreaks indicate that a community could be heading for an outbreak — and what action the public should then take — is also unclear.

“I don’t think we have much experience with that as a nation yet,” Howard said. She said the purpose of the report, which is sent to members of Congress and other policymakers, is to draw attention to the need for standardization in wastewater monitoring.

“Once you’ve standardized, the next question is how do we use the data we collect to make policy decisions,” she said. “And again, I don’t think as a public health community there’s still a good sense of what these numbers should be telling us and what we should be doing.”

Utah was one of the first states to test sewage for the virus, launching a pilot project shortly after the pandemic began more than two years ago and now collecting samples twice a year. week at sites representing about 88% of the state’s population, Nathan LaCross said. , Utah Department of Health’s Wastewater Surveillance Officer.

The Centers for Disease Control and Prevention tracks wastewater monitoring data from more than 750 sites, though few have up-to-date data and are scattered across 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 said a new wastewater monitoring website is in the works to better present trends identified by what he called a “statistical process”, acknowledging that there is “no super scientific method to gauge just how alarming these trends are.

Maddi Crezee receives a sample of raw sewage at the Salt Lake City Water Reclamation Facility in Salt Lake City on Wednesday, April 6, 2022. Water from 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, described the state’s current reports of the results of the analysis of what Utahns are flushing down the toilet as frustrating, especially to lay people. Even as an epidemiologist, Kim said it was difficult for him to know from the available data when there was a real surge in cases.

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

The doctor said the map showing fluctuations in COVID-19 levels at the wastewater treatment sites where the samples are collected is the type of information that is particularly useful to the public because it is “visibly easy to recognize in terms of geography where we start to see the hotspots.

But even combined with the “more granular data” that’s more useful to epidemiologists and other professionals, like the number of millions of gene copies per person per day, Webb said wastewater monitoring isn’t the only way to keep tabs on COVID-19.

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

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

While that means most Utahans don’t see new data until Thursdays, Webb said it’s important to recognize that public health officials and other decision makers still have access to information collected daily. on the virus.

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

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