Polioviruses found in wastewater samples in 2 N.Y. counties, suggesting continued spread

New York state health authorities revealed Thursday that they had detected additional polioviruses in wastewater sampled in two counties north of New York City, findings that signal continued spread of the viruses in the region.

The positive wastewater samples were found in Rockland County, where health authorities revealed two weeks ago that a man in his 20s had been paralyzed by so-called vaccine-derived polioviruses, and in neighboring Orange County as well. Positive samples were collected in June and July in Orange County and in July in Rockland County, suggesting that viruses have been spreading for some time.

Rockland and Orange counties have among the lowest vaccination rates for polio in New York state. Only 60% of young children in Rockland County have had the three doses of polio vaccine they should have received by their second birthday; in Orange County, the rate is 59%. While positive wastewater samples haven’t been reported from nearby Sullivan County, it too has a dismal polio vaccination rate for 2-year olds, 62%.

Those low vaccination rates suggest young children in all three counties are at risk of contracting polio if they remain unvaccinated.

“As we learn more, what we do know is clear: the danger of polio is present in New York today,” Mary Bassett, the state health commissioner, said in a press release. “We must meet this moment by ensuring that adults, including pregnant people, and young children by 2 months of age are up to date with their immunization — the safe protection against this debilitating virus that every New Yorker needs.”

Bassett said the state health department will continue to conduct wastewater surveillance.

Kim Thompson, president of the non-profit Kid Risk and a mathematical modeler who has worked for years on polio eradication, said there could be more paralytic polio cases in New York state.

“The chances of becoming paralyzed are small, but I think this case shows us that they’re not zero,” she said.

“We shouldn’t have polio in the United States 22 years after the original target for polio eradication.”

The global effort to eradicate polio — wipe it from the face of the earth — has been underway since 1988. The goal was to finish the job by the year 2000. But polio is a wily foe and though the global eradication program has come close on a couple of occasions, wild polio continues to circulate in pockets of western Pakistan and eastern Afghanistan.

Late last year, viruses from Pakistan made their way to Malawi, where a child was paralyzed. Further spread had occurred since, with Mozambique reporting four cases in 2022.

Cases of wild polio, however, are low, numbering only 18 so far this year. The bigger problem at this point are vaccine-derived viruses, which are spreading in larger numbers and over wider terrain.

Genetic analysis of the viruses in the positive wastewater samples in New York was conducted by the Centers for Disease Control and Prevention and revealed they are linked to the viruses that paralyzed the Rockland County man. His virus, in turn, was discovered to be linked to vaccine-derived viruses detected in sewage in Jerusalem and London.

Vaccine-derived polioviruses come from the oral polio vaccine Albert Sabin developed in the 1950s. The United States stopped using this vaccine in 2000, meaning these viruses had to have made their way to this country in a person or persons infected with them elsewhere.

Sabin’s vaccine was made using live but weakened versions of all three polioviruses, types 1 through 3. Vaccinated children shed the vaccine viruses in their stools and, in places where hygiene levels are not high, the vaccine viruses can spread to other unvaccinated children in a household or neighborhood. Over time, though, if they continue to find unvaccinated children to infect, they can regain the power to paralyze. Biologically the illness they trigger is the same as that caused by wild polio.

Most people who are infected with polio will have no symptoms; some will suffer mild illness. But it is estimated that out of every 1,000 infections, between one and five people will develop neurological disease — either meningitis or some form of paralysis. The latter is typically irreversible.

Since it stopped use of oral vaccine, the United States has exclusively relied on injectable vaccine that is made with inactivated polioviruses. The vaccine viruses in IPV, as it is known, cannot paralyze or transmit from person to person.

The evidence of circulating polioviruses underscores the importance of increasing vaccine uptake in the affected region. That could be a challenge. Rockland County has a large population of Hassidic Jews who resist vaccination for philosophical reasons. This part of New York state experienced a large and protracted measles outbreak in 2018-2019, fueled by vaccine resistance in these communities.

“Any unvaccinated children and adults should receive a first polio immunization immediately,” Rockland County Health Commissioner Patricia Schnabel Ruppert said in a statement.

The state department of health also suggested adults who are unvaccinated, who don’t know their polio vaccination status, or who are partially vaccinated — they haven’t received three doses — should be vaccinated.