Surveillance of wastewater systems proved useful during the COVID-19 pandemic and merits further investment to respond to future threats, according to a new report from the National Academies of Sciences, Engineering, and Medicine (NASEM).
But there’s room for improvement. The report highlights five core pillars for developing a stronger National Wastewater Surveillance System (NWSS), calling for a system that is “flexible, equitable, integrated, actionable, and sustainable.”
In 2020, the CDC launched the NWSS in response to the COVID-19 pandemic, as these systems can flag biomarkers of infection in municipal sewer systems — including DNA or RNA — and track trends or emerging variants, according to a NASEM press release.
Given the rise in at-home testing, where results are rarely communicated to public health systems, wastewater surveillance has gained even more relevance, said Guy Palmer, PhD, of Washington State University in Seattle and chair of the committee that authored the report, during a webinar on Thursday.
It is also useful because it is unaffected by the availability of tests, test-seeking behavior, and access to health facilities, he added.
As of fall 2022, these systems can now track over a third of the U.S. population, said Palmer.
“Critically, the data consistently leads hospitalization data,” he said, noting that it was not uncommon for surveillance data to serve as a “warning signal” to hospitals, allowing them to delay elective surgeries to preserve beds in intensive care units ahead of a predicted surge.
However, the current distribution of wastewater surveillance is uneven, not fully representative, and not equitable, Palmer said, given that these systems are developed based on an “initial willingness to participate.”
The Future of Surveillance
A future NWSS should be able to track multiple threats at once, and “pivot quickly to new threats,” the report noted. Such surveillance has already helped to track other diseases besides COVID-19, including polio and monkeypox outbreaks just last year, said Palmer, and can also be used to screen for antibiotic resistance.
The report calls on the CDC to establish an “open and transparent process” for determining potential targets of surveillance, based on three criteria: “(1) public health significance of the threat, (2) analytical feasibility for wastewater surveillance, and (3) usefulness of community-level wastewater surveillance data to inform public health action.”
Asked whether existing surveillance systems are able to detect novel threats, or are “pathogen-agnostic,” committee member John Scott Meschke, PhD, also of the University of Washington, said most of the systems “target very specific pathogens.”
With regard to equity, the committee stressed that such a future NWSS should cover a mix of demographics, “engage underrepresented communities,” and have the capacity to extrapolate these findings where possible to communities that do not have sewer systems.
Palmer noted that the homes of 16% of the U.S. population are not connected to a wastewater treatment plant, but that these individuals could still be tracked through work or school buildings that do connect to treatment plants.
With regard to systems being actionable, wastewater surveillance data has recently been used to help determine where pop-up vaccination and testing clinics were needed, said Palmer.
And of course such a system must be “operationally and fiscally sustainable,” he said. The top reason localities shared for not participating in surveillance is the “burden” required in terms of expertise and staffing, he added.
The committee has urged the CDC to “work to reduce the financial and capacity barriers,” Palmer said. “The effectiveness of the national system will depend on predictable and sustained federal investment,” he added.
Additionally, the committee also proposed establishing “sentinel sites,” such as international airports or other ports of entry, zoos, and farms to detect emerging pathogens sooner.
Privacy Concerns
While surveillance systems do give rise to concerns over privacy, Palmer said the committee felt that because of the aggregated nature of the data, “the benefits of wastewater surveillance outweigh existing privacy concerns.”
Regardless, the CDC has recommended convening an ethics advisory committee that will “clearly communicate how the data are used and not used,” Palmer said, and ensure a “strong firewall” with law enforcement.
According to the committee, however, surveillance data have been used to map substance abuse — which is of interest to law enforcement and to public health officials. So that “firewall” is more specific to repurposing data in order to identify specific individuals who may be violating the law, said committee member Michelle Mello, JD, PhD, of Stanford Law School and Stanford School of Medicine.
Individuals can’t be identified from wastewater samples, but “technology changes,” said Palmer, and so data-sharing policies will need to be revisited over time.
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