Optimizing Wastewater Surveillance: The Necessity of Standardized Reporting and Proficiency for Public Health

Wastewater-based surveillance (WBS) has emerged as a valuable tool for public health, allowing a greater understanding of disease prevalence in communities. With historical significance in monitoring polio transmission,¹ WBS gained further prominence in 2020 by enhancing the population-level monitoring of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) trends.^2,3 Since then, WBS has been used to track diseases such as influenza,⁴ respiratory syncytial virus,⁵ norovirus,⁶ and mpox. The global implementation of WBS signifies its movement from a research initiative to a staple public health tool, which is especially critical for virus monitoring. However, the diverse methodologies adopted for WBS present challenges. Although each method may address specific stakeholder needs, the lack of standardized reporting guidelines and external validation limits the scope and utility of the data.

A key advantage of WBS is that it enables public health authorities at the state and federal levels to determine where to allocate resources, ideally before a wider spread outbreak. Data aggregation is possible only when metrics such as target concentration and recovery are reported in the same concentrations and with similar driving calculations. This concern is amplified when data from a variety of methods are aggregated at a state, national, or global scale. Therefore, our objective is to promote standardized reporting guidelines in WBS as a critical part of a public health framework.

PROVIDING REAL-TIME ACTIONABLE DATA

WBS provides real-time data on targets (chemical or microbial) to support clinicians, public health response, and the public in general. It can provide an early warning for diseases, as individuals can begin shedding pathogens such as viral particles and microbial cells when they are asymptomatic or presymptomatic.^7,8 It can also provide insight into the presence and transmission of an infection. Historically, WBS has most prominently been implemented for monitoring polio transmission.¹ WBS for SARS-CoV-2 monitoring during the COVID-19 pandemic provided a similar complementary framework for monitoring community disease prevalence when clinical testing was not yet widely available.²

Genomic sequencing of target pathogens in wastewater has also proven useful for tracking emerging viral variants of concern and for providing clinicians and public health organizations with information on variants circulating in their community.⁹ Furthermore, WBS has improved the ability to develop seasonal viral models for a community. Seasonal models based on clinical data are already established for influenza, but these models do not exist for other viral targets, including respiratory syncytial virus, norovirus, and hepatitis A virus, which is a critical gap in understanding that WBS can fulfill.

WBS enables a dynamic response to a disease outbreak and can be easily pivoted for new and emerging diseases faster than the production of clinical tests. WBS enables public health authorities to have real-time, preclinical data to enable preventive responses in potentially at-risk communities. It can also be used to make sure emergency response personnel have all the necessary personal protective equipment and response tools if called. Thus, WBS fills a previously existing gap in the arsenal of disease-monitoring capabilities.

UNIQUE POPULATION-LEVEL DATA

WBS is fundamentally different from traditional public health testing methods. WBS data can be quantitative, rather than binary, enabling the measurement of the abundance of the pathogen or compound in wastewater. These data allow the direct measurement of a target gene or genes rather than needing to rely on clinical presentation of a disease. WBS captures an integrated sample from the sewered population that can indicate overall disease presence and abundance in a community. It may be particularly useful when traditional public health monitoring is not sensitive enough or there is insufficient infrastructure or funding for traditional public health testing. However, each disease will need to be evaluated for its suitability for WBS monitoring because of variance in shedding rates, persistence in the sewer network, and specificity of the target (primer and probe design). Because of all of these qualities, WBS is a good fit for early detection of outbreaks, tracking the tail end of an outbreak, or seasonal increases and decreases in pathogens in a population. WBS is an important tool to complement, not replace, traditional public health monitoring.

BENEFITS OF PROFICIENCY TESTING

Quality data on disease incidence in a community improve public health monitoring because of increased actionability and confidence. There is potential to adopt similar external quality assessment procedures from the well-established clinical laboratory framework. Accreditation of clinical proficiency testing programs involves a blind analysis on a standardized sample set that is processed identically to real-world samples. Upon submission of the results, the laboratory receives a report that includes the laboratory’s results compared with the anticipated values from the reference standard, as well as any necessary corrective actions the laboratory must undertake. Laboratories are routinely reassessed at predefined intervals via externally validated proficiency testing to promote sustained accuracy.

In the United States, the Clinical Laboratory Improvement Amendments maintain and enforce a minimum standard for accuracy, reliability, and quality of laboratory testing focused on the diagnosis, treatment, and prevention of disease. This standard is achieved primarily through workflow-specific evaluations of proficiency and accuracy with a known ground truth as a point of comparison. Efforts in WBS are challenged in this regard because it is difficult to know the absolute concentration of the target, making a ground truth impossible. Laboratory accreditation frameworks exist, including the International Organization for Standardization 17025 framework, which dictates general requirements for testing competency and calibration; however, these are not widely required for public health laboratories. International Organization for Standardization 17025 is a great starting point for all laboratory accreditation, but it will not replace WBS-specific proficiency testing.

The National Institute for Standards and Technology Standards for Wastewater Surveillance Working Group has been developing physical and documentary standards to aid in wastewater surveillance (e.g., development of a DNA standard for mpox assay validation, evaluation of synthetic wastewater for ground truth molecular applications).¹⁰ Current efforts for proficiency testing in WBS have been led by the Ontario Clean Water Agency, which conducts comparative interlaboratory testing on a common sample.¹¹ Furthermore, the European Union has set a precedent for WBS accreditation with the establishment of the Sewage Core Analysis Group Europe in 2010.¹² This international collaboration gathers multilaboratory WBS data from more than 100 European cities and towns, offering a publicly accessible repository of WBS information as a public health service and resource.

To participate in the Sewage Core Analysis Group Europe program, a laboratory or program must successfully undergo a blind proficiency test, akin to the assessments employed by US clinical laboratory service providers. Using these established resources and expertise could expedite the development of a similar system in the United States. Box 1 synthesizes elements from existing Clinical Laboratory Improvement Amendments and Environmental Protection Agency drinking water microbiology analysis as elements that are critical for reporting.

BOX 1—

Existing Clinical and Environmental Proficiency and Reporting Standards and Their Identified Relevance to Wastewater-Based Surveillance (WBS)

Sample Processing Stage	Relevant CLIA Recording Requirements13	Relevant EPA Laboratory Certification for Microbiology in Drinking Water14	WBS Applicable Parameters
Preanalytic sampling and transport	Sample location, time, date, sample storage and preservation, conditions for transportation	Site location, sample type, name of sampler, date and time, chain of custody	Sample location, time, date, sample storage and preservation, conditions for transportation
During sample processing	•Control procedures and corrective action to take when calibration or controls fail, reportable range for test results in the test system as established •Reference or typical intervals •Established system for where to enter results for a specific test or step in the workflow	•Date and time of analysis •Inclusion and analysis of controls, including positives and negatives •Method conducted •Laboratory and signature of person performing analysis	•Date and time of analysis •Inclusion and handling of positive and negative controls •Method conducted •Laboratory and signature of person performing analysis
Reporting	•Results reported from collected data •Test report date and assays run •Pertinent “normal” values	•Maintain records for 5 y, including raw data calculations and quality control data	•Results reported from collected data •Report raw data, calculations, and quality control data

Note. CLIA = Clinical Laboratory Improvement Amendments; EPA = Environmental Protection Agency.

Currently, WBS laboratory processes operate without a federally mandated regulatory framework. Although the National Wastewater Surveillance System (NWSS) currently serves as the primary data repository for WBS data in the United States, it relies on self-reported data that practitioners generate without external validation. In the process of developing these programs, it is crucial to strike a balance between establishing a regulatory framework to uphold data quality and ensuring that the demands on WBS laboratories are not unduly onerous.

The expenses associated with laboratory accreditation processes ultimately contribute to the per sample cost for end users. This expense raises the concern of potentially offsetting the cost-effectiveness that is currently a fundamental advantage of the WBS process. The establishment of an external standardized evaluation framework and proficiency testing is an essential step in the evolution of the field, particularly as WBS continues to gain traction and expand its future analytical capability.

REPORTING GUIDELINES

Developing data that are comparable across districts and time points is critical for building a robust monitoring network and enables individual laboratories to track performance as they improve or expand their targets of interest. Comparable data also allow data aggregation and reuse as well as a well-informed regional public health response. Most recommendation guidelines have focused primarily on the comparability of generated data and not on the actionability that additional data collection can provide. Both of these are key elements that are needed to maximize the utility of WBS.

Guidelines exist for environmental monitoring via digital PCR (polymerase chain reaction) and qPCR (quantitative PCR); however, these guidelines do not focus on a public health–based framework^15,16 These stakeholder-developed guidelines have promoted workflow transparency in environmental monitoring while facilitating method innovation. However, researchers have repeatedly identified the need for these practices to be enforced by journals as well as data repositories to ensure they are followed. Although these guidelines are not focused on a public health–based framework, best practices and lessons learned from them could serve to inform the development of WBS reporting guidelines, as was suggested by McClary et al.¹⁷ This framework can be modified to remain target neutral while also incorporating elements of environmental sampling known to affect reported concentrations.

Reporting for WBS in the United States is heavily driven by programs such as NWSS. In addition to reporting what NWSS requires, which includes laboratory processing steps, including concentration method, nucleic acid extraction method, and recovery, laboratories should include any additional data or metadata critical for public health authorities to generate actionable insights. Common, open reporting guidelines would serve to clarify and standardize what (e.g., units) should be reported and how (e.g., concentrations). WBS implementers must strike a balance between speed, data quality assurance and quality control, and actionability. Reporting guidelines that cover the entire WBS workflow must be easily accessible to laboratories and, ideally, should be streamlined across organizations within a country and across countries for global surveillance efforts.

Global efforts such as the public health environmental surveillance open data model can aid in generating interoperable data-handling pipelines across sites.¹⁸ Furthermore, reporting will improve WBS quality if the model can provide more information about the collected sample, including metadata (e.g., weather conditions, which can affect sewage dilution rate) and the exact sample collection point for sewershed mapping.

CHALLENGES TO STANDARDIZATION

Every sewer system is unique because of factors such as its size, demographics served, location, age, and sewer contributors, making standardizing WBS a daunting task. Moreover, WBS programs and monitoring laboratories have constraints that affect monitoring frequency, number of sampling points, and methodologies. This is further compounded by challenges such as supply chain shortages that can lead to using method substitutes. The inherent variety present in WBS systems and data generation further emphasizes the critical role that proficiency testing programs could play in WBS. Many methods can generate valid WBS results¹⁹; therefore, verifying that a laboratory is applying its selected method of choice accurately can greatly help to improve the robustness and utility of generated data.

Method-specific guidance must also be developed to guide new WBS implementers away from common pitfalls. The National Institute of Standards and Technology and Technology Standards for Wastewater Surveillance Working Group is working to develop high-level guidelines for the most common WBS methodologies to aid in this effort. This, in conjunction with common reporting guidelines, will aid in pushing WBS to new discoveries. Providing best practices for data and metadata reporting will facilitate comparable, reusable data and lay the foundation for future methodological standards when the field is ready for them.

THE FUTURE IS BRIGHT

We are just beginning to realize the extensive public health benefits of WBS, particularly in terms of tracking disease prevalence and guiding targeted public health interventions. In addition, WBS is being expanded to monitor the prevalence of antimicrobial resistance genes in wastewater to support the global fight against antibiotic and antimicrobial resistance. Although we have focused here on microbial targets, WBS has been applied to chemical targets for applications such as illicit drugs, indicators of vaccinations for rate measurement, antiretrovirals, and medicines used for home management of disease. An integration of microbial and chemical WBS will enable the expanded application of WBS in public health and will usher in a more advanced understanding of targets, such as pathogens (e.g., SARS-CoV-2, Coxsackievirus) and antiretroviral medications (e.g., Paxlovid, efavirenz). Reporting guidelines and proficiency testing could be expanded to encompass chemical targets in addition to microbial targets to facilitate the integration of multiple data types to address complex public health issues.

The types of laboratories performing WBS have expanded since the start of the COVID-19 pandemic, enhancing the capability of WBS. Initially, the testing laboratories reporting to NWSS included primarily academic, environmental, and private sector organizations. As the pandemic progressed, public health laboratories and health departments developed the capability to operate in the WBS space. Such laboratories are now equipped to monitor wastewater for targets as well as to analyze and interpret data. This expansion of participants in NWSS and WBS in general highlights the importance of the requirements for data reporting and data validation to be streamlined across organizations, easily accessible, and nonlaborious to be adopted throughout the field. The development of standards for WBS requires a community-driven effort with input from all key stakeholders. We have focused on reporting guidelines here, but standards are needed to support the full WBS workflow. Different types of standards, such as consensus-based documentary standards and reference materials, can be used in concert to support WBS.

CONCLUSIONS

WBS is a valuable public health tool that can be strengthened by the integration of external validation frameworks and reporting guidelines. It provides novel data that can inform the public health response. The diversity of individuals and organizations participating in WBS strengthens the field, as it introduces new viewpoints and utility for monitoring targets.