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Polio Wastewater Monitoring

What is wastewater, and where does it come from?

Wastewater is sewage that contains human stool (feces) that has been flushed down the toilet along with other water that goes down household drains. Wastewater is managed in the sewage system and treated at wastewater treatment plants.

What is wastewater monitoring?

Wastewater monitoring is an important public health tool that can provide early and ongoing detection of polio in communities. This monitoring can help identify where the virus may be and when, although it does not provide detailed information about who or how many people or households may be infected.

Polio is highly contagious, and people can spread the virus even if they don't know they're sick. However, individuals infected with polio shed virus in their stool. Wastewater samples – which are based on water from sewage systems – collect, test, and treat feces (poop particles) flushed down the toilet. This makes wastewater monitoring an important tool to identifying poliovirus among both asymptomatic (not sick) and symptomatic (sick) people.

How does wastewater monitoring work?

MDHHS works with a network of partners to collect wastewater samples. Once samples are collected, laboratory partners conduct PCR testing for poliovirus. All results are then reported to MDHHS and the corresponding local health department. Any positive detections of poliovirus in wastewater by PCR are considered preliminary, and those samples will be sent to CDC for confirmatory genetic sequencing.

What are the results of the wastewater findings?

As of November 15, 2023, wastewater testing for polio has ended. Poliovirus was not detected in any of the Oakland County wastewater samples tested from June-November 2023. Since there were no detections of poliovirus at these sites, wastewater testing has been discontinued. It may be restarted if additional cases are detected in the United States or if new data indicates that more widespread poliovirus transmission is a concern. Public Poliovirus Results Table.

What do these results mean for Michiganders?

  • If vaccine-derived poliovirus, which could result in illness, is found in wastewater, this would indicate that someone in that community is shedding poliovirus that could infect and cause disease in an unvaccinated person.
  • If found, the concern is that the virus is being detected in communities that may have low vaccination rates with many individuals at risk for becoming infected and developing polio.
  • For example, the recent paralytic polio case (in New York) occurred in a person who was unvaccinated and lives in a community with low vaccination rates, where poliovirus could spread easily.
    • The clinical and public health recommendations remain the same. Our robust routine vaccination program and monitoring have proven effective in protecting Americans from polio. In this response, vaccination against polio is prioritized for communities at-risk and those who may be under-vaccinated.
    • Even if there were no further detections in wastewater, the recommendation would remain to keep childhood vaccination rates strong across the country. In the United States, population immunity to paralytic polio is maintained through high rates of polio vaccination coverage during routine infant and childhood immunization.
  • Since poliovirus was not detected in wastewater at the Michigan sampling locations, these findings indicate that, in those locations, the likelihood of there being an infected person who is shedding poliovirus is extremely low. This data, combined with no reports of suspect clinical cases of polio in Michigan and no additional positive polio cases in New York state, is encouraging.

Which counties are included in the wastewater testing for polio?

Wastewater monitoring in Michigan took place at two locations in Oakland County from June-November 2023. This county was chosen based on an existing wastewater monitoring infrastructure, pockets of lower polio vaccination coverage, and historical vaccine-preventable disease outbreaks.

Are there privacy concerns with wastewater monitoring?

A major advantage of wastewater monitoring as a source of data is that it is entirely anonymous and cannot be used to trace back to individuals or households. Wastewater sampling occurs at a treatment plant or access point, which provides a sample representative of an entire community or population and does not allow for identification of individual information.

How do we know wastewater cannot contaminate public sources of water, including drinking water, streams, and lakes?

Wastewater (sewage) goes to a community wastewater treatment plant, whereas drinking water, including tap water, comes from a public water system – which wastewater does not interact with.

A public water system is an entity which provides water to the public for human consumption through pipes or other constructed conveyances. The term human consumption includes water used for drinking, bathing, showering, cooking, dishwashing, and maintaining oral hygiene.

How can I learn more about wastewater monitoring happening in Michigan and around the world?

Learn more about Michigan’s wastewater monitoring for other diseases, such as COVID-19: Wastewater Surveillance for COVID-19 (

Michiganders can visit this page to learn more about New York State's wastewater surveillance programing

Visit the Global Polio Eradication Initiative (GPEI) and the Global Polio Laboratory Network (GPLN) to access information from the World Health Organization (WHO) and CDC.

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Last updated December 12, 2023