Top 5 Takeaways

1. Effective Detection of Mpox in Wastewater: The study revealed a sensitivity of 32% in detecting a single mpox case in large population samples through wastewater surveillance. Sensitivity improved with more cases in the community.
2. High Predictive Values: The positive and negative predictive values (PPV and NPV) for detecting mpox in wastewater were high, indicating reliable detection capabilities.
3. Public Health Implications: An isolated detection of Monkeypox virus in wastewater suggests a limited public health response is needed, while nondetection in a monitored community indicates a low likelihood of widespread cases.
4. Sensitivity Variances: The sensitivity of wastewater surveillance increased as the number of persons shedding the virus increased, reaching 77% for detecting 15 or more cases.
5. Complement to Case Surveillance: Wastewater surveillance is a valuable tool to complement traditional mpox case surveillance, especially in guiding public health responses to outbreaks.

Original Article Author and Citation

Corresponding Author

Carly Adams, PhD – cadams3@cdc.gov

Suggested Citation

Adams C, Kirby AE, Bias M, et al. Detecting Mpox Cases Through Wastewater Surveillance — United States, August 2022–May 2023. MMWR Morb Mortal Wkly Rep 2024;73:37–43.DOI: http://dx.doi.org/10.15585/mmwr.mm7302a3

Summary

This report assesses the performance of wastewater surveillance in detecting mpox cases in the United States. The Centers for Disease Control and Prevention’s (CDC) National Wastewater Surveillance System began testing for Monkeypox virus in wastewater in October 2022. The study evaluated the sensitivity, positive predictive value (PPV), and negative predictive value (NPV) of this surveillance method by comparing wastewater detections with reported mpox cases.

Methods

Data from August 2022 to May 2023 were analyzed, involving 3,492 wastewater samples from 89 sites across 26 counties. The analysis compared Monkeypox virus detection in wastewater with the number of people shedding the virus in each county, assuming complete case ascertainment and a shedding duration of 25 days post-symptom onset.

Discussion

Wastewater surveillance showed varying sensitivity based on the number of shedding individuals, with higher detection rates as the number of cases increased. This method offered a high PPV and NPV, suggesting its reliability in detecting mpox cases in large populations. Notably, the surveillance was sufficiently sensitive to detect even a single case, highlighting its effectiveness compared to surveillance for other viruses like SARS-CoV-2.

Conclusion

The study concludes that wastewater surveillance is an effective method for detecting mpox cases, providing valuable support to traditional case surveillance. It helps guide public health responses, especially in determining the presence or absence of mpox cases in large communities.

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