why it matters
Wastewater monitoring can be an effective way to detect community-level outbreaks and other health threats. It has the potential to identify a COVID-19 outbreak 1-2 weeks earlier than clinical testing and enable a faster public health response. However, the lack of national coordination and standardized methods poses challenges for wider adoption.
What is that? Wastewater monitoring, also known as wastewater-based epidemiology, involves monitoring for pathogens (e.g., viruses), as well as pharmaceuticals and toxic or other chemicals by testing waters worn (see fig. 1). Public health officials can use this approach to monitor outbreaks, identify threats (e.g., antibiotic-resistant bacteria) and, in response, support resource mobilization.
Figure 1. Uses of wastewater testing.
Pathogens and chemicals can enter sewers through human waste. Wastewater monitoring programs collect samples of wastewater from these systems and treatment plants and send them to laboratories for analysis. Officials can use test data, for example, to assess whether there is a viral outbreak or an increase in drug use, and then decide what action to take to protect public health. These actions may include increasing clinical testing in an area or alerting local clinics and hospitals to prepare for an increase in patient numbers.
How is it used? For many years, the United States and other countries have used wastewater monitoring to monitor levels of pathogens and chemicals in their communities. Australia, for example, uses a sewage monitoring program to track the amounts of illicit drugs consumed in the population in order to estimate the effectiveness of law enforcement efforts to seize drugs.
In the United States, federal and local governments, universities, and businesses have recently increased their investments in wastewater monitoring in response to the COVID-19 pandemic. As of February 2022, health departments in 43 jurisdictions, representing approximately 16% of the U.S. population, were using funds distributed by the Centers for Disease Control and Prevention (CDC) to support wastewater monitoring efforts. The CDC is working with these 43 jurisdictions to collect data that tracks levels of SARS-CoV-2 and make this data publicly available through its National Wastewater Surveillance System (NWSS) website. Nearly 80 percent of the US population is served by municipal sewer systems that could be monitored through such programs.
Wastewater monitoring can serve several purposes (see Fig. 2). For example, it can provide early warning for infectious disease outbreaks so that a community can take action. It can detect low levels of SARS-CoV-2 in human waste before symptoms appear, as early as 1-2 weeks before an infected person can seek clinical testing. It can also detect SARS-CoV-2 in asymptomatic people who represent around 70% of cases and may not seek clinical testing.
Figure 2. Benefits of wastewater monitoring for different population sizes.
Some US universities have used sewage monitoring to identify buildings, such as dormitories, with potentially high or rising infection rates among resident students and then target clinical testing and quarantine efforts to prevent outbreaks. on the campus. For example, in the fall of 2020, a university used sewage monitoring to detect nearly 85% of COVID-19 cases that were later confirmed by clinical testing.
What are the gaps? Wastewater monitoring can have enormous potential as a public health tool, but some aspects of the science may need further development. For example, rainwater or industrial discharges can dilute wastewater samples, while contaminants such as animal waste can compromise sample origin or quality. In January 2021, for example, scientists identified a SARS-CoV-2 mutation in New York City wastewater, potentially signifying a variant, but are still trying to determine if it has circulated in humans.
Additionally, the potential cost savings of wastewater monitoring are unclear. At least one study suggests that wastewater monitoring could save countries millions, if not billions, of US dollars, depending on several country-specific factors. However, the general lack of cost-benefit analyzes makes it difficult to determine how and when to use it.
What are some concerns? Some scientists argue that the United States could benefit from a standardized approach to wastewater monitoring. For example, testing different variants of SARS-CoV-2 in wastewater is not common practice. Some state health departments do, but the CDC does not use NWSS to track variants found in wastewater. Additionally, the lack of a standardized approach complicates efforts to aggregate, interpret, and compare data across sites and develop large-scale public health interventions.
Some scientists suggest extending the NWSS beyond SARS-CoV-2 to identify other pathogens and chemicals. For example, searching for chemicals, such as opioids, in wastewater requires different processes than searching for pathogens. A system like the NWSS could be designed to identify a variety of health threats.
Finally, sewage monitoring raises privacy and ethical issues because sewage not only contains a pathogen’s genetic data that allows public health officials to identify the pathogen, but also human genetic data that could potentially be misused. Additionally, communities can be stigmatized if wastewater monitoring data indicates the spread of pathogens or illicit drug use.
- Faster public health response. Healthcare providers and public health officials can use wastewater monitoring as an early warning of health threats and use it with other tools to predict, prepare for, and initiate faster response to disease outbreaks. infectious diseases and other health threats.
- Community orientation. Local testing could provide an opportunity to monitor and respond to the spread of pathogens and drug use, especially in areas where access to testing or health care is limited.
- Affordability. Wastewater monitoring can be particularly useful where clinical trials are resource-limited, but quantifying the value is difficult due to a lack of cost-benefit analyses.
- Coordination and standardization. Methods for collecting samples, analyzing and sharing data are not currently standardized, making it difficult to compare sites and focus mitigation efforts.
- Sample integrity. Contaminants such as animal waste can compromise sample quality, and the origin of detected pathogens and chemicals may not always be clear.
- Privacy. The use of wastewater data could pose privacy issues when linked to identifiable data, especially in small communities.
Policy Context and Issues
- What steps could help standardize wastewater monitoring programs in the United States?
- What can be done to promote cost-benefit analyzes of widespread wastewater monitoring to detect threats to public health?
- If the costs and benefits are favorable, what policies would best facilitate the use of wastewater monitoring data while protecting the privacy of individuals?
- How can wastewater surveillance data be used as a public health resource for policy-making?
For more information, contact Karen Howard at 202-512-6888 or [email protected]