Surveillance: Watching What’s in the Wastewater

Wastewater surveillance, also known as wastewater-based epidemiology (WBE), is increasingly recognized as a powerful tool for public health. It offers an early warning system for various infectious diseases and aids in predicting outbreaks. Our interest in this critical area was particularly piqued by a recent incident in North Carolina, where the detection of mpox viral particles in wastewater samples prompted health officials to issue an alert, even before clinical cases of that specific clade were reported. This compelling real-world example, highlighted in a recent press release from our client, GeoVax, underscored the immediate relevance and potential of WBE. It motivated us to delve deeper into how this innovative approach works and to share our findings here.

This method leverages the fact that many pathogens, or their genetic material, are shed by infected individuals (even those who are asymptomatic) into the wastewater system through feces, urine, or other bodily fluids.

How Wastewater Surveillance Works

1. Shedding of Pathogens: Individuals infected with certain viruses or bacteria—such as SARS-CoV-2 (the virus causing COVID-19), influenza, RSV, or even poliovirus—shed genetic material (DNA or RNA) or whole pathogens into their bodily waste. This shedding can occur even before symptoms appear or in individuals who never develop symptoms, making it a valuable early indicator.
2. Collection of Wastewater Samples: Wastewater utilities collect samples of untreated municipal wastewater from various points within the sewer system, typically at wastewater treatment plants. These samples represent a pooled aggregate of waste from thousands, or even millions, of people connected to that specific sewershed (the geographic area served by a particular sewer system).
3. Laboratory Analysis: The collected wastewater samples are transported to laboratories for analysis. Advanced molecular techniques, primarily quantitative polymerase chain reaction (qPCR) and genomic sequencing, are used to detect and quantify the presence of specific pathogen genetic material.
   • qPCR: This method amplifies specific DNA or RNA sequences, allowing scientists to determine the concentration of a pathogen in the sample. Higher concentrations generally indicate more widespread infection in the community.
   • Genomic Sequencing: This goes a step further, allowing researchers to identify specific variants or strains of a pathogen (e.g., new SARS-CoV-2 variants or, as in the North Carolina case, a specific clade of mpox) and track their prevalence.
4. Data Interpretation and Public Health Action: The laboratory results are then analyzed and interpreted by public health officials. This information helps them:
   • Detect Early Trends: Wastewater data can show increases or decreases in disease trends days to weeks before they are observed through clinical testing or healthcare visits. This is particularly crucial for asymptomatic cases that might not seek medical care.
   • Complement Clinical Data: WBE provides a community-level snapshot, independent of individual testing behaviors, healthcare access, or testing availability. It complements clinical surveillance data, offering a more complete picture of disease spread.
   • Predict Outbreaks and Inform Response: By monitoring changes in pathogen concentrations and identifying emerging variants, public health officials can anticipate potential outbreaks, allocate resources (e.g., testing sites, vaccination campaigns), and implement targeted public health interventions (e.g., public health messaging, mask mandates).
   • Monitor Antimicrobial Resistance: Wastewater can also be analyzed for the presence of antibiotic-resistant genes, providing insights into antimicrobial resistance trends within a community.

Credible Articles and Key Insights

• Centers for Disease Control and Prevention (CDC) National Wastewater Surveillance System (NWSS): The CDC has been instrumental in establishing and promoting wastewater surveillance, especially during the COVID-19 pandemic. Their website provides comprehensive information on how WBE works, current data for various pathogens (COVID-19, influenza, RSV, mpox), and its role in public health. They highlight that wastewater data can provide “early indications of changes in community levels of SARS-CoV-2, as well as emerging variants of the virus, sometimes weeks ahead of other public health data.”
  • Reference: https://www.cdc.gov/nwss/how-wws-works.html
• North Carolina Department of Health and Human Services (NCDHHS) Press Release on Mpox Detection: The NCDHHS issued a press release on April 22, 2025, detailing the detection of Clade I mpox viral particles in wastewater samples in Greenville, NC. This was particularly significant as Clade I mpox had not been previously reported in North Carolina, demonstrating wastewater surveillance’s ability to identify the presence of a pathogen before clinical cases are confirmed.
  • Reference: https://www.ncdhhs.gov/news/press-releases/2025/04/22/mpox-found-wastewater-north-carolina-ncdhhs-urges-public-and-providers-be-alert
• National Academies of Sciences, Engineering, and Medicine Reports: Reports commissioned by the CDC, such as “Wastewater-based Disease Surveillance for Public Health Action,” provide in-depth analysis of the benefits, challenges, and future of WBE. They emphasize its value beyond COVID-19 for various infectious diseases and its ability to capture pre-symptomatic and asymptomatic cases.
  • Reference: https://www.ncbi.nlm.nih.gov/books/NBK591714/
• “Wastewater surveillance as a sentinel for disease” (UNEP): This article highlights that wastewater sampling has been used for a long time to detect diseases like polio and has expanded significantly since COVID-19. It emphasizes WBE’s ability to “cost-effectively gauge the extent to which a disease might be circulating in a community, without solely relying on data from people using health services.”
  • Reference: https://www.unep.org/technical-highlight/wastewater-surveillance-sentinel-disease
• “Wastewater-based epidemiology as surveillance and early warning of infectious disease outbreaks” (ResearchGate/PubMed): Several review articles delve into the potential of WBE as an early warning system. They emphasize that “the biological principle underlying wastewater as a leading indicator is that many infected individuals excrete the virus in biological samples before they develop symptoms, and thus before seeking medical care.”
  • Reference: https://www.researchgate.net/publication/341300170_Wastewater-based_epidemiology_as_surveillance_and_early_warning_of_infectious_disease_outbreaks
  • Reference: https://pubmed.ncbi.nlm.nih.gov/32395676/
• “Advances in Wastewater-Based Epidemiology for Pandemic Surveillance: Methodological Frameworks and Future Perspectives” (MDPI): This recent review underscores WBE’s role in “transforming pandemic surveillance from reactive containment to proactive population health management.” It discusses advancements in pathogen detection technologies (qPCR and metagenomics) and predictive modeling.
  • Reference: https://www.mdpi.com/2076-2607/13/5/1169

Key Advantages for Outbreak Prediction

• Early Detection: Pathogen shedding can occur before clinical symptoms, allowing for earlier detection of increasing cases.
• Population-Level Data: Provides a broad overview of community infection trends without relying on individual testing or healthcare-seeking behavior.
• Detection of Asymptomatic Cases: Captures infections in individuals who may never get tested or seek medical care.
• Identification of Variants: Genomic sequencing allows for tracking of emerging and circulating variants of concern.
• Cost-Effective and Efficient: A single sample can provide information for a large population, making it more efficient than widespread individual testing.
• Privacy-Preserving: It collects aggregate data, avoiding individual identification.

While wastewater surveillance is a powerful tool, it’s most effective when integrated with other public health surveillance systems to provide a comprehensive understanding of disease spread and inform public health decisions.