Feb 4, 2022 - Health

CDC to expand wastewater surveillance program in bid to better track COVID

Photo of two people in PPE squatting over two containers of sample bottles at a wastewater plant
Wastewater control inspectors retrieve sewage samples, which are sent to labs to detect the presence of COVID, in Oakland, California on July 14, 2020. Photo: Paul Chinn/The San Francisco Chronicle via Getty Images

The Centers for Disease Control and Prevention (CDC) announced Friday that it will expand a program that detects the coronavirus in wastewater as part of an effort to better track infection trends across the U.S.

Why it matters: Roughly 40-80% of people with COVID-19 shed viral RNA in their feces, according to CDC estimates. That makes wastewater surveillance a critical tool for monitoring the virus' spread.

How it works: Shedding the virus in feces starts "very early" after someone gets infected before tailing off, said Amy Kirby, team lead for the National Wastewater Surveillance System.

  • "It’s in fact, one of the first signs that we see of infection, which is really important for this early warning capability for wastewater," Kirby said at a briefing Friday. "We see those rates go up very, very high."
  • These increases typically occur before corresponding increases in clinical cases, Kirby added.

Driving the news: The CDC's program, which picks up on infections from people with or without symptoms, is currently operating with over 400 sites. In the next few weeks, an additional 250 sites are expected to begin providing data as well.

  • This information will be made available to the public for the first time on the CDC's COVID data tracker.
  • Users will be able to see changes in wastewater virus levels over the previous 15 days for each participating community, as well as the percentage of positive tests from the last 15 days, Kirby said.

What they're saying: "These built-in advantages can inform important public health decisions, such as where to allocate mobile testing and vaccination sites," Kirby said.

  • "Public health agencies have also used wastewater data to forecast changes in hospital utilization, providing additional time to mobilize resources and preparation for increasing cases."
  • The program still has limitations, especially in communities with transient populations or minimal sewer infrastructure, and should be used in combination with case-based surveillance, Kirby noted.
  • But many cities and counties are already "using their wastewater testing to better understand the trajectory of a surge of infections," Kirby added. "Now more communities will have the opportunity to use this tool to help guide their public health decision making."
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