Want to know if a COVID-19 wave is heading to your town? Check the poop.
The Centers for Disease Control and Prevention said Friday it is expanding efforts to sample wastewater for the virus and is posting data from its national surveillance network for the first time on its online COVID-19 tracker.
“It allows you to compare data across states directly,” said Amy Kirby, the program lead for CDC’s National Wastewater Surveillance System.
The CDC says infected people can shed the coronavirus in their feces even if they don’t show symptoms. The viral RNA can be detected in wastewater when it is sampled from a treatment plant.
Screening the sewer system allows public health officials to get a sense of whether the virus is surging or easing in a specific area and dispatch limited resources to where they are needed. It is also a way to track the virus without depending on individuals to seek out testing or go to the doctor when they are sick.
Scientists say wastewater surveillance serves as an early-warning system for communities. It often detects increasing levels of the virus in the sewer system four to six days before cases pop up through clinical settings.
Ms. Kirby said 400 sites in the U.S. are reporting wastewater samples to the CDC as part of coronavirus tracking efforts. The agency expects 250 more sites to join in the next few weeks, and it is working with officials in 37 states to bring additional sites online in the coming months.
“We will not have a look into every state but we will have a look into most states as well as territories and tribal communities,” Ms. Kirby said.
Only some of the participating sites have updated their data recently enough to display results on the online tracker.
Academic researchers and local utilities began testing wastewater for the virus in a kind of grassroots effort early in the pandemic. Universities deployed it regularly to try and detect outbreaks in dormitories.
The CDC launched its national surveillance system in September 2020. Officials said they are now collecting enough data to make an online tracker useful to the public.
Efforts to increase the network’s footprint come at a critical juncture in the pandemic. States are trying to put the emergency phase behind them and treat the virus as a manageable disease — while also hoping they are nimble enough to respond to seasonal surges.
The wastewater surveillance will detect increasing cases “as soon as we can, so we can have those extra days for communities to prepare their hospital systems for pending cases,” Ms. Kirby said.
It will also help communities know what’s going on as people pivot to at-home testing. Those results are not reported to health authorities as frequently as those from labs.
Ms. Kirby said the surveillance network will be useful beyond COVID-19. The CDC is hoping to use it to track food-borne illnesses like norovirus or influenza by the end of this year.
What may seem like an experiment in excrement has a long track record. Wastewater surveillance has been used for decades, particularly overseas, to track and eradicate polio.
Ms. Kirby said the surveillance is designed to complement, and not replace, efforts to track the virus through clinical testing.
There are limits to using wastewater to track viral trends. Some parts of the country are heavily reliant on septic tanks instead of an interconnected sewer system, and wastewater surveillance isn’t that useful in places with a lot of tourists or otherwise transient populations, because the samples are supposed to reflect persons who may be infectious while they mingle in a specific community.
Federal disease-trackers say there is no evidence of someone getting sick from being exposed to the virus through untreated wastewater.
Health, The New York Today