Sewage Data Added to CDC's COVID Tracker for Early Surge Warnings

— Hundreds more wastewater detection sites to add data soon

MedpageToday
The National Wastewater Surveillance System logo over a close up photo of waste water at a treatment plant.

A new federal data tracker showing where community sewage systems are detecting increases in COVID-19 viral RNA is providing the nation with a sense of "situational awareness" as an early warning system for coming surges as well as new variants of interest, CDC announced Friday.

Amy Kirby, PhD, MPH, the lead for the CDC's National Wastewater Surveillance System, said the tracker now contains information from 400 testing sites in 37 states and will soon expand with another 250 locations and will include several territories and tribal communities.

She called the data "uniquely powerful, because they capture the prevalence of infections from people with and without symptoms," regardless of whether they have access to healthcare services or clinical testing.

"The real power of this program will be more evident in coming weeks when hundreds more testing sites will begin submitting data," thus offering public health officials a better understanding of COVID-19 trends in those communities, Kirby said.

The tracker now reflects information from 34,000 samples representing 53 million people in 37 states for the last 15 days and is updated daily.

An important benefit is that the tracker allows communities to see where the virus is showing up, whether quantities are increasing or decreasing, and in which nearby communities or nearby states. It is additionally useful as increasing numbers of people use at-home tests rather than going to a testing center to determine if they are infected with COVID-19, she said.

Public health officials can use that information to get a head start in anticipation of viral surges, make decisions about where to send mobile testing sites or send additional hospital supplies, or prepare for hospital capacity issues, Kirby noted.

It is also useful to track future variants of concern.

"Should there be a new pathogen of interest, we could ramp up the system within a few weeks to start gathering community-level data on that new pathogen," she said.

The project was started in September 2020 by academic institutions and wastewater utility systems to look for viral shedding in feces, which is detectable very early during the course of infection before symptoms appear. Now, Kirby said, the CDC has enough reliable data in the system to make it available to the public.

The CDC is working to expand the wastewater surveillance platform to look for antibiotic-resistant, foodborne, and fungal pathogens.

Kirby said that wastewater systems collect samples through an auto sampler, or personnel just grab a sample by dipping a bottle into the wastewater flow. A lab concentrates viruses, extracts genetic material, and uses PCR to measure how much of the virus is in the sample.

Asked about the finding in New York City sewage of "cryptic variants," as reported by researchers in Nature Communications Thursday, regarding mutations that had not been reported in human patients and whether those samples signaled a new viral threat, Kirby said the CDC is "not tracking cryptic lineages but is in contact with the researchers who published that paper and are watching that work very closely."

The researchers speculated that these viral mutations are coming from virus-infected animals, perhaps rats, or from people whose infections were not captured by traditional sequencing methods.

Of course, the wastewater tracker cannot be used in communities that have no sewer systems, and is not as useful in communities with high rates of tourism or transient populations.

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    Cheryl Clark has been a medical & science journalist for more than three decades.