Poliovirus found in samples of wastewater in New York state have been genetically linked to the case of polio that resulted in an unvaccinated man becoming paralyzed earlier this year.

New York health officials reported in July that a case of polio had been detected in Rockland County.

This was the first U.S. case of polio detected in nearly a decade. In September, New York Gov. Kathy Hochul (D) declared an emergency over the detection of polio in wastewater.

More than a thousand wastewater samples were collected from Rockland County and Orange County in New York. Of all the samples, 89 collected from 10 sewersheds tested positive for poliovirus type 2 (PV2). The samples were collected between March and October of 2022.

The Centers for Disease Control and Prevention (CDC) noted that wastewater testing can help identify where a virus is circulating, but stated that the most important public health action was to improve vaccine coverage in the area and to detect cases through the surveillance of symptoms.

The current wastewater surveillance suggests that there could be “some level of community transmission” for PV2 in Orange, Rockland and Sullivan counties, according to the CDC.

Previous samples from Kings, New York and Queens counties also indicate that PV2 could be circulating in those counties as well, though testing has been somewhat limited in those areas.

“At least five New York counties had evidence of a sustained period of community transmission of poliovirus in 2022. Unvaccinated and undervaccinated persons in these areas are at risk for infection and paralytic disease,” said the CDC.

The agency called for the maintenance of a “robust” system of surveillance for acute flaccid myelitis (AFM), a neurological condition that causes weak muscles and reflexes and can result in paralysis of the limbs. While polio can cause paralysis, AFM can be the result of many viruses that commonly circulate in the U.S. and polio must often be ruled out in such cases.

It was reported last week that the CDC was considering an oral polio vaccine to help combat the emergency in New York. The agency has warned that several hundred undetected cases of polio could be circulating in the community where the July case was first detected.

Most people who are infected do not display symptoms, but can still pose a risk to those who are immunocompromised or unvaccinated.