The poliovirus that paralyzed an unvaccinated New York man in July is still spreading

The same strain of poliovirus that paralyzed an unvaccinated young man in New York’s Rockland County this summer is still circulating in several areas of the state as of early October, according to wastewater monitoring study released by the Centers for Disease Control and Prevention on Friday.

The finding suggests the virus continues to pose a serious threat to anyone in the area who is unvaccinated or undervaccinated. The three counties with persistent transmission—Rockland, Orange, and Sullivan—have alarmingly low vaccination rates.

In Rockland, for example, one county zip code has a polio vaccination rate among children under 2 of just 37 percent, according to government data. In Orange, the ZIP code has a vaccination rate of just 31 percent. The countywide vaccination rates for Rockland and Orange are 60 percent and about 59 percent, respectively.

Sullivan County has not provided ZIP code-level vaccination rate data to the state. But in August press releaseCounty Public Health Director Nancy McGraw suggested some areas of the county had low levels similar to Rockland and Orange.

“Sullivan County has an overall 62.33 percent polio vaccination rate, but there are some areas of the county with lower vaccination rates, and because polio can spread very easily, it’s important that everyone gets vaccinated,” McGraw said at the time . “Public health offers a safe and proven vaccine available for children two months of age or older. We are working with the state to provide vaccine to adult providers. If adults need a vaccine, we encourage them then [sic] to contact their healthcare provider.’

Most adults and children in the US are vaccinated against polio. Since 2000, the country has relied on inactivated polio vaccine (IPV), which is given in three doses before the age of 24 months, with a fourth injection between the ages of 4 and 6. Only the first three doses are 99 percent to 100 percent effective in preventing polio, however, and vaccination rates report the percentage of 2-year-olds who followed the recommended vaccination schedule for the first three vaccines.

Risk Assessment

But in low-vaccination pockets, such as those in several New York counties, poliovirus—in this case, a revertant virus derived from an oral vaccine used abroad that is transmitted among unvaccinated people—can continue to spread. In the new CDC study released today, health officials sifted through sewage surveillance data to see where and how widespread this spread is.

They looked for poliovirus among 1,076 samples taken from 48 sewer sheds serving Rockland and 12 surrounding counties between March 9, 2022 and October 11, 2022. A total of 89 (about 8 percent) samples taken from 10 sewer sheds tested positive for poliovirus . Of the 89 samples, 82 were from counties outside of New York, collected from sewer facilities in Nassau, Orange, Rockland, and Sullivan counties. Of these 82 positive samples, 81 were genetically related to the Rockland County patient, and one, which was from Orange County, did not have adequate genetic data to determine a relationship.

The remaining seven of the 89 positive samples were from New York, one of which was linked to the Rockland case, and five were of insufficient quality to determine a link. Interestingly, one was from a different poliovirus unrelated to the Rockland case, suggesting that more than one strain of poliovirus was introduced to the US.

The strain of poliovirus in the Rockland case is genetically related to viruses circulating in London and Israel.

The fact that samples from October 4, 5 and 6 tested positive for the poliovirus, which has already paralyzed one person, suggests others are still at risk in the US.

“[A]all unvaccinated or undervaccinated adults or children living or working in Kings, Orange, Queens, Rockland, or Sullivan counties, New York should complete the IPV series now,” the study authors concluded.