CDC Surveilling CO Wastewater To Track COVID Trends

COLORADO — The Centers for Disease Control and Prevention said Friday it’s adding data collected from sewage samples around the country to its COVID-19 Data Tracker, providing a more complete picture of trends in participating communities and putting them at the frontier of infectious disease surveillance.

The National Wastewater Surveillance System was created by the CDC to better track the presence of COVID-19 by analyzing wastewater samples.

The surveillance system has been operating since September 2020, but the CDC added it to the tracker last week as another tool to compare virus trends across states, Dr. Amy Kirby, who is leading the effort, told reporters Friday.

There are eight locations reporting data from Denver, Adams, Arapahoe and Boulder counties. Each location shows a decrease of 10-99 percent over the last 15 days, as of Monday afternoon. Two of the locations in Boulder are showing the same absolute change, but one is showing a decrease of 0-9 percent, and another is reporting an increase of 1-9 percent.

There are five locations reporting data in Larimer county, each of which shows the same 10-99 percent drop in virus detected. Two additional locations in El Paso County and one additional location in Pueblo county are all reporting drops between 10 and 99 percent.

The CDC is providing the change in the levels of COVID-19 in wastewater rather than the actual concentrations of COVID-19 in each location, as laboratory methods used to estimate concentrations might differ slightly. Percent change is a system of quantification that is comparable across these different methods, officials said.

The surveillance database shows changes in the virus level in wastewater over the previous 15 days for each participating community. The tracker also provides the percentage of COVID-19 tests from the past 15 days that are positive.

Kirby said an estimated 40 percent to 80 percent of people infected with COVID-19 shed viral RNA in their feces, “making wastewater and sewage an important opportunity for monitoring the spread of infection.”

The tool also can provide an early warning of outbreaks on the horizon.

‘So what we see is shedding in feces starts very early after someone is infected,” Kirby said. “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.

“We see those rates go up very, very high,” she said. “So lots of virus [is] shed into feces very early in the infection, and then it tails off.”

The surveillance system, which was started by researchers and a few public utilities, has become a nationwide system with more than 34,000 samples collected from approximately 53 million Americans.

Currently, the CDC is helping support efforts to implement the system in 37 states, four cities and two territories, Kirby said, and more than 400 testing sites around the country have already begun collecting samples.

At least 250 sites will come online in the next few weeks, she said.

Kirby said the “real power” of the surveillance system will be demonstrated when hundreds more testing sites begin submitting data. What makes it particularly powerful, Kirby said, is that it detects infections in people who may not have had a clinical test.

“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.”

This is the first U.S. government-sponsored use of wastewater surveillance, though it’s a commonly used public health tool in other countries, Kirby said.

“Wastewater surveillance has been used for many decades, actually, to track polio in communities, not in the U.S., but definitely overseas as part of the polio eradication efforts,” she said. “And they use it essentially the same way we do — so to look for communities [where] polio is circulating and then use that as a trigger for additional clinical surveillance in those communities.”

The CDC is working to expand the National Wastewater Surveillance platform to gather data on other pathogens — including E. coli, salmonella, norovirus influenza and the emerging fungal pathogen Candida auris — perhaps as soon as the end of the year, Kirby said.