Wastewater Surveillance

What is wastewater, and where does it come from?

Wastewater is sewage that contains feces that have been flushed down the toilet and other water that goes down household drains. Wastewater is managed in the sewage system and treated at wastewater treatment plants.

Wastewater collected in sewer systems in New York cannot be a source of polio infection or transmission for the general public. It does not contaminate New York drinking water, including tap water, streams, and lakes.

What is wastewater surveillance?

Wastewater surveillance is an important public health tool, providing the early and ongoing detection of polio in communities. This monitoring helps identify where the virus may be and when, though it does not provide quantitative 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 our sewage system – collect and treat feces flushed down the toilet. This makes wastewater surveillance critical to identifying poliovirus among both asymptomatic and symptomatic people.

How does wastewater surveillance work?

NYSDOH works with a network of partners to collect and store wastewater samples. Once samples are collected, NYSDOH and its partners work with CDC, who conduct PCR testing for poliovirus and perform sequence analysis to understand if polio is present, if the type of poliovirus present is of concern, and if the strain identified is genetically-linked to the case of paralytic polio identified in Rockland County. All samples reported are samples of concern, meaning they are types of poliovirus that can cause paralysis in humans.

What are the results of the wastewater findings so far?

As of March 22, 2023, sequencing analysis by the Centers for Disease Control and Prevention (CDC) confirmed the presence of poliovirus in a total of 101 positive samples of concern:

  • Of the 101 positive samples of concern, 94 samples have been found to be genetically linked to the individual case of paralytic polio among a Rockland County resident.
  • Of the 94 samples, 45 samples were collected in Rockland County, 30 samples were collected in Orange County, 13 samples were collected in Sullivan County, 5 samples were collected in New York City, all of which were from Brooklyn (Kings County), with 4 of these in an area that contains an adjacent portion in Queens County, and 1 sample was collected in Nassau County.
  • Of the 45 samples identified in Rockland County, 2 were collected in May, 3 were collected in June, 9 were collected in July, 21 were collected in August, 7 were collected in September, 2 were collected in October, and 1 was collected in February 2023.
  • Of the 30 samples identified in Orange County, 2 were collected in June, 5 were collected in July, 6 were collected in August, 9 were collected in September, 6 were collected in October, 1 was collected in November, and 1 was collected in December.
  • Of the 13 samples identified in Sullivan County, 2 were collected in July, 5 were collected in August, 5 were collected in September, and 1 was collected in October.
  • Of the 5 samples identified in New York City, 4 were collected in August, and 1 was collected in October.
  • The sample identified in Nassau County was collected in August.
  • 7 positive samples of concern, 1 collected in April from Orange County and 2 collected in June and 4 collected in July from New York City have also been identified. While at this time, these samples have not been genetically linked to the individual case in Rockland County, sequencing analysis characterizes these samples as either a vaccine-derived poliovirus (1, collected in New York City in July) or variants of the revertant polio Sabin type 2 poliovirus (6, 3 collected in July and 2 collected in June in New York City; 1 collected in April in Orange County). Both of these types of polioviruses can cause illness, including paralysis, in humans.

For more detailed findings, see the latest polio wastewater surveillance report (PDF).

NYSDOH will continue its wastewater surveillance efforts in partnership with CDC and communicate openly with New Yorkers as more information is available.

What do these results mean for New Yorkers?

These environmental findings provide evidence that the unvaccinated individual Rockland County resident with paralytic polio contracted the virus through local—not abroad or international—transmission and provide evidence of expanding community spread. This underscores the urgency of every adult and child, particularly those where poliovirus has been identified, getting immunized and staying up to date with their polio immunization schedule.

New Yorkers should know that these environmental findings do not indicate that the individual in Rockland County was the source of the transmission, and case investigation into the origin of the virus is ongoing.

When did NYSDOH begin wastewater surveillance?

NYSDOH developed a wastewater surveillance network for COVID-19. Following the identification of a case of paralytic polio in an unvaccinated individual in Rockland County, this network was adapted to include testing for polio. Wastewater surveillance is an active, ongoing effort that NYSDOH is leading in partnership with local, national, and global public health authorities.

Which counties are included in the wastewater surveillance testing for polio?

Wastewater surveillance is an active, ongoing effort which includes both proactive sampling and, to be as extensive as possible, collecting and testing available retrospectively stored samples. The focus of this programming began where the individual case of paralytic polio was identified in Rockland County and the surrounding areas, and these efforts will continue and expand.

Are there privacy concerns with wastewater surveillance?

A major advantage of wastewater surveillance 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 surveillance happening in New York and around the world?

New Yorkers can learn more about New York State's wastewater surveillance programing here. More information about the work of the Global Polio Eradication Initiative (GPEI) and the Global Polio Laboratory Network (GPLN)—which includes the World Health Organization (WHO) and CDC—is available .