Your City’s Sewage May Reveal Its Gut Health, Study Finds

Wastewater surveillance made headlines during COVID-19 as a way to track outbreaks before anyone showed up at a clinic. A new study suggests the same sewage samples could do something far broader: reveal how healthy an entire community's gut microbiome is, and how that lines up with everything from hypertension to unemployment.

Sewage Samples From Eight Ohio Cities Reveal Distinct Gut Signatures

Researchers Emma Lancaster and Jiyoung Lee collected influent wastewater, the raw sewage arriving at treatment plants before any processing, from eight Ohio cities between May and June 2022. Because that wastewater is essentially a pooled sample of everything residents flush, it carries a community-level snapshot of the gut bacteria living inside the local population, without needing to swab a single individual.

Using bioinformatic processing and multivariate statistics, including principal component analysis and multiple linear regression, the team characterized each city's collective gut bacterial profile and compared it against publicly available health, lifestyle, and socioeconomic data for those same communities. The eight cities turned out to have genuinely distinct microbial fingerprints, with meaningful variation in taxa like Bacteroidota, Desulfobacterota, Verrucomicrobiota, Akkermansia, Desulfovibrio, and Streptococcus, the kinds of bacteria researchers already associate with gut inflammation, metabolic health, and diet.

Gut Bacteria Signatures Track With a Community's Chronic Disease Burden

The more striking finding is what those bacterial differences correlated with. Several microbial features, including the phylum Firmicutes, the genus Desulfovibrio, the genus Acetobacterium, and overall bacterial diversity, were significantly associated with community-level rates of smoking, obesity, unemployment, and minority status. Zooming out further, multiple microbial variables tracked with a wider set of public health indicators: hypertension, high cholesterol, asthma, obesity, smoking, depression, and unemployment all showed statistical associations with specific features of a city's sewage-derived gut profile.

Rural communities in the study stood out in particular, showing both higher rates of adverse health outcomes and distinct microbiome signatures compared with more urban areas. That pattern fits a broader body of research on rural health disparities, but seeing it show up in bulk gut bacteria data adds a new, easily collectible layer of evidence to that story.

A Retrospective, City-Level Design Extends Wastewater Surveillance Beyond Infectious Disease

Wastewater-based epidemiology has mostly been used for tracking infectious disease outbreaks and drug use trends, not chronic disease or mental health. This study is part of a small but growing effort to push that toolkit further, treating sewage as a cheap, continuous, and already-existing data stream for population-level health surveillance rather than building expensive new individual testing programs from scratch.

The appeal for public health officials is obvious: instead of relying on self-reported surveys or waiting for costly individual biomonitoring, a city could theoretically track shifts in its collective gut health, and by extension its metabolic and inflammatory disease burden, by regularly sampling the sewage it already has flowing through its treatment plants.

The Findings Are Correlational, Not Proof That Gut Bacteria Drive These Outcomes

The core limitation here is baked into the study's design. This is a retrospective, cross-sectional analysis at the level of entire cities, not individuals, so it can only show that certain gut bacteria signatures and certain health indicators tend to show up together in the same places. It cannot show that a city's gut microbiome profile is causing its rates of hypertension or depression, rather than both being downstream of shared factors like diet, income, or access to health care. The wastewater was also sampled during a narrow two month window in a single state, so it is not yet clear how well these specific associations would generalize to other regions, seasons, or years.

There is also an inherent ceiling on precision with this method: wastewater microbiome data reflects an entire population blended together, so it cannot distinguish which specific residents are driving a given signal, and it says nothing about any one person's own gut health.

Next Steps for Turning Sewage Into a Public Health Surveillance Tool

The obvious next step is replication across more cities, more seasons, and ideally multiple years, to see whether these community-level associations hold up over time or were specific to Ohio in the summer of 2022. Researchers interested in wastewater-based epidemiology will also want to pair these gut microbiome signals with more granular local health data, and eventually test whether tracking shifts in a city's sewage microbiome over time can actually predict changes in disease burden, rather than just correlating with a single snapshot.

If that pans out, it would hand public health departments a genuinely novel, low-cost early warning system, one already sitting in the pipes underneath every city, that could help target interventions toward the communities that need them most. Related work has already shown wastewater gut microbiome data can flag community-level obesity risk, and broader efforts to build geospatially resolved public health surveillance from wastewater sequencing suggest this Ohio study is part of a wider shift in how sewage gets used as a public health tool, one that Science recently covered as pollution and human health increasingly get tracked through sewage microbes.

References

1. Emma Lancaster, Jiyoung Lee (2026). Wastewater-Based Human Gut Microbiome Surveillance Links Microbial Signatures to Population Health in Ohio Communities. Environmental Research. https://doi.org/10.1016/j.envres.2026.125332
2. Jiangping Wu, Yan Chen, Jiawei Zhao, et al. (2024). Associations between wastewater gut microbiome and community obesity rates: Potential microbial biomarkers for surveillance. Soil & Environmental Health. https://doi.org/10.1016/j.seh.2024.100081
3. Braden T. Tierney, Jonathan Foox, Krista A. Ryon, et al. (2024). Towards geospatially-resolved public-health surveillance via wastewater sequencing. Nature Communications. https://doi.org/10.1038/s41467-024-52427-x
4. Elizabeth Pennisi (2015). Pollution, human health tracked with sewage microbes. Science. https://doi.org/10.1126/science.aab0269