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CDC to expand wastewater monitoring to help track coronavirus trends

The agency plans to use the system to find other deadly pathogens

The Ballenger-McKinney wastewater treatment facility in Frederick, Md. (Katherine Frey/The Washington Post)
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The Centers for Disease Control and Prevention plans to expand a system that detects the coronavirus in wastewater to better predict surges and declines of the virus and, eventually, wants to harness the network’s early-warning power to find other deadly pathogens and control outbreaks of food-borne disease.

Research suggests that 40 to 80 percent of people infected with the coronavirus shed viral genetic material in their feces even if they don’t have symptoms. It’s one of the first signs of an infection.

Increases in wastewater virus levels generally take place four to six days before health officials see a corresponding rise in case counts or hospitalizations.

“These data are uniquely powerful because they capture the presence of infections from people with and without symptoms and are not affected by access to health care or availability of clinical testing,” Amy Kirby, who leads the agency’s wastewater surveillance system, said during a briefing Friday.

Wastewater surveillance can be used to track other diseases and health concerns, Kirby said. Officials are working to expand surveillance to gather data on other pathogens by the end of the year, with targets including antibiotic-resistant bacteria, norovirus, influenza, a deadly fungal pathogen called Candida auris and food-borne infections caused by E. coli and salmonella.

In response to the pandemic, the agency launched a national wastewater surveillance system in September 2020. Sewage surveillance has been used for years around the world to identify polio outbreaks. Several other countries, including France, Germany and the Netherlands, have been monitoring sewage systems for the coronavirus.

The CDC gets data from about 400 testing sites that measure the coronavirus in wastewater. Some health departments are also able to conduct advanced genetic sequencing to track variants of concern. California, Colorado, New York City and Houston were the first to detect evidence of the omicron variant in community wastewater.

Participating states have used wastewater data to make public health decisions, Kirby said, such as directing mobile testing to certain vaccination sites and readying additional equipment and other resources for hospitals in communities where cases are forecast to increase.

Universities, colleges, states and cities, and commercial testing companies collect samples from sewage pipes to monitor the spread of the virus. Cities including Boston were able to identify impending case surge and conclude that the omicron variant had peaked.

The CDC until 2020 did not have a national system to track infectious diseases through wastewater. The agency has since provided money to 37 states, four cities and two territories for utilities to collect sewage samples, for laboratories to get those samples tested and for state officials to send the data to the CDC. Many of these states are still implementing their systems.

On Friday, the CDC said it was making public on its website the data it has received from 28 states and the District of Columbia. Some states have that data available on their websites, but the CDC data allows consumers to compare data across states.

More than 34,000 samples have been collected from communities representing about 53 million people. The CDC plans to add 255 testing sites in the next few weeks and additional sites during the next few months, expanding the reach of the program “to look into most states” and territories and tribal communities, Kirby said.

Kirby said her team is working with the rest of the agency’s coronavirus response to “find ways that wastewater surveillance can help provide situational awareness for what’s going on in the community, as well as serving as that early warning system that a new increase may be coming in a community.”

In Ohio, a color-coded map on the state health department’s website shows the increase or decrease in virus levels in wastewater for an area. Substantial increases in virus levels trigger an email notification to health districts, utilities and community health leaders, according to a CDC report last fall.

In Utah, wastewater data is one of the main components of a ranking system to determine where to dispatch mobile testing teams.

Out of 255 surveillance systems with data, 70 percent showed a decline in the virus over the past 15 days, while the remainder reported increases. No clear patterns emerged from the data, and in many cases treatment plants showing increases are next to plants with decreases.

Dan Keating contributed to this report.

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