Science and Technology Highlight: Wastewater Monitoring

Why is this important

Wastewater surveillance can be an effective way to detect community-wide disease outbreaks and other health threats. It has the potential to identify a COVID-19 outbreak one to two weeks before clinical testing and allow for a faster public health response. However, the lack of national coordination and standardized methods pose challenges to wider adoption.

Science

What is that? Wastewater monitoring, also known as wastewater-based epidemiology, is the monitoring of pathogens (eg viruses), as well as drugs, toxic chemicals or other chemicals by testing wastewater (see Figure 1). Public health officials can use this approach to monitor outbreaks, identify threats (for example, antibiotic-resistant bacteria), and, in response, support resource mobilization.

Figure 1. Wastewater testing uses.

Pathogens and chemicals can enter sewage systems through human waste. Wastewater monitoring programs collect wastewater samples from these systems and treatment plants and send them to laboratories for testing. 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 actions 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 patients.

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 wastewater monitoring program to track the amounts of illicit drug use among the population to estimate the effectiveness of law enforcement efforts to control 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 about 16 percent of the US 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 SARS-CoV-2 levels and make this data publicly available through the National Wastewater Surveillance System (NWSS) website. Nearly 80 percent of the US population is served by municipal sanitation systems that can be monitored through such programs.

Wastewater monitoring can serve many purposes (see Figure 2). For example, it can provide early warning of an infectious disease outbreak so that the community can take action. It can detect low levels of SARS-CoV-2 in human feces before symptoms appear, as early as one to two weeks before an infected person requests clinical tests. It can also detect SARS-CoV-2 from asymptomatic individuals who make up about 70 percent of cases and may not seek clinical testing.

Figure 2. Wastewater surveillance benefits from different population sizes.

Some US universities have used wastewater monitoring to identify buildings, such as dormitories, with high or increasing rates of infection among resident students and thus target clinical testing and quarantine efforts to avoid outbreaks on campus. For example, in the fall of 2020, one university used wastewater monitoring to detect nearly 85 percent of COVID-19 cases that were subsequently confirmed by clinical testing.

What are some of the loopholes? Wastewater monitoring may have tremendous potential as a public health tool, but some aspects of the science may need further development. For example, rainwater or industrial discharge can dilute wastewater samples, while pollutants such as animal waste can affect sample source or quality. In January 2021, for example, scientists identified a SARS-CoV-2 mutation in New York City wastewater, which may indicate a variant, but they are still trying to determine whether it is spreading between humans.

In addition, the potential cost savings from wastewater monitoring are unclear. At least one study indicates that wastewater monitoring could save countries millions to billions of US dollars, depending on several country-specific factors. However, the general lack of cost-benefit analytics makes it difficult to determine how and when to use them.

What are some concerns? Some scholars assert that the United States could benefit from a standardized approach to wastewater control. For example, testing different SARS-CoV-2 variants in wastewater is not standard practice. Some state health departments do this, but the CDC does not use the NWSS to track the variants present in wastewater. Furthermore, the lack of a standardized approach complicates efforts to collect, interpret and compare data across sites and to develop public health interventions at scale.

Some scientists suggest expanding the NWSS beyond SARS-CoV-2 to identify pathogens and other chemicals. For example, testing chemicals, such as opiates, in wastewater requires different processes than testing for pathogens. A system like NWSS can be designed to identify a variety of health threats.

Finally, wastewater monitoring raises privacy and ethical concerns because wastewater contains not only the genetic data of pathogens that allow public health officials to identify the pathogen, but also human genetic data that can be misused. In addition, communities may be stigmatized if wastewater monitoring data indicate the spread of pathogens or illicit drug use.

chances

  • Faster overall health response. Healthcare providers and public health officials can use wastewater monitoring as an early warning of health threats, and use it in conjunction with other tools to predict, prepare for, and initiate a faster response to infectious disease outbreaks and other health threats.
  • Focus on the community. Local testing can provide an opportunity to monitor and respond to pathogen prevalence and drug use, particularly in areas with limited access to testing or health care.

Challenges

  • Affordability. Wastewater monitoring can be particularly useful when clinical testing is resource-limited, but value is difficult to determine due to a lack of cost-benefit analyses.
  • Coordination and unification. Methods for sample collection, analysis, and data sharing are not currently standardized, making it difficult to compare sites and focus mitigation efforts.
  • sample integrity. Contaminants such as animal droppings can compromise sample quality, and the origin of the pathogens and chemicals detected may not always be clear.
  • Privacy. The use of wastewater data may raise privacy concerns when linked to identifiable data, especially in small communities.

Policy context and questions

  • What steps might help standardize wastewater monitoring programs in the United States?
  • What can be done to enhance cost-benefit analyzes of large-scale wastewater surveillance of public health threats?
  • If costs and benefits are favorable, what policies would make it easier to use wastewater monitoring data while protecting individual privacy?
  • How can wastewater monitoring data be used as a public health resource for policy making?

For more information, contact Karen Howard at 202-512-6888 or [email protected]

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