(NEXSTAR) – For years, the Centers for Disease Control and Prevention has tracked various health measures across the United States. Among the most recent is poo, which is being surveyed to keep tabs on the prevalence of COVID-19.
Scientifically speaking, the CDC monitors wastewater in dozens of communities, mostly in the Midwest and New England. In September 2020, the CDC launched the National Wastewater Surveillance System, which works with local health departments to track SARS-CoV-2.
By using data from wastewater testing areas, health officials can respond better and faster to the spread of COVID-19. During a Feb. 4 telebriefing, NWSS team leader Dr. Amy Kirby noted that the surveillance system had collected more than 34,000 samples representing approximately 53 million Americans.
How it works
According to the CDC, people infected with SARS-CoV-2, the virus that causes COVID-19, can shed genetic material from the virus in their stool. This genetic material, or RNA, can then be detected in wastewater, which includes water from toilets, showers and sinks.
Wastewater from participating sewage basins – the area served by a sewage collection system – is collected as it flows through a treatment plant. Samples are sent to environmental or public health facilities to be tested for SARS-CoV-2. Health departments then submit the test data to the CDC where it is analyzed to assess the presence of COVID in the community.
By measuring levels of SARS-CoV-2 in wastewater over time, the CDC says public health officials can determine whether infections are increasing or decreasing within their community.
Sewage monitoring isn’t new either – according to Kirby, officials abroad have led similar efforts to eradicate polio.
Where wastewater is tested
Communities in Texas, Illinois, Michigan, California and Oregon are among those conducting sewage testing. The other participating states are Wisconsin, Ohio, Missouri, New York, Virginia and North Carolina.
The CDC is currently helping 34 states, four cities, and two territories develop wastewater monitoring systems while more than 400 sites have already begun work. In early February, Kirby said the NWWS had a commercial testing contract that would provide twice-weekly testing to an additional 500 sites.
According to the CDC, sewage testing is not able to capture data from every home or major facility. Houses that rely on a septic tank, for example, are not included in community-level monitoring. Neither prisons, nor universities, nor hospitals that treat their own waste.
Wastewater treatment plants that pre-treat wastewater before it reaches the plant are also unavailable monitoring sites.
Where to see the data
While sewage monitoring has been ongoing since the start of the pandemic, the CDC has only just made the data it collects available to the public. If wastewater monitoring is ongoing in your community, your local health department likely also has a publicly available dashboard.
For national data, the CDC uses a color-coded chart to show the 15-day percent change in levels of SARS-CoV-2 found in surveyed wastewater. Those who saw a decreased change in SARS-CoV-2 prevalence appear blue while those who see an increased change are shades of orange or red. Communities marked with a gray dot have no recent data available.
As of February 17, most communities reporting sewage monitoring data are noted with blue dots, signifying that a drop in SARS-CoV-2 has been detected.
On the CDC map, you can also see the proportion of detections over 15 days within the participating communities. According to the CDC, this is calculated over a 15-day window by dividing the number of tests in which SARS-CoV-2 was detected by the total number of tests for all sewer sheds sampled.
As seen on the CDC map, not all states conduct sewage monitoring. Kirby explained earlier this month that the agency was working to add more test sites in the coming weeks.
Outside of COVID, Kirby noted that they are working to expand NWWS to collect data on other pathogens, saying, “Our targets include antibiotic resistance, foodborne infections, like E. Coli, salmonella, influenza norovirus and the emerging fungal pathogen, Candia Auris. ”
She explained that once the infrastructure is in place to collect samples, submit them to a lab, and share data with the CDC, adding tests for other pathogens can be done “pretty quickly.” . Additionally, wastewater monitoring could be used for non-infectious diseases, such as drug addiction.
According to Kirby, this type of monitoring “requires more technical analysis and technical development.”