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The same strain of polio virus that paralyzed an unvaccinated young man in New York’s Rockland County this summer is still spreading in several parts of the state as of early October, according to a wastewater monitoring study released Friday by the Centers for Disease Control and Prevention. has been published.
The finding suggests that the virus continues to pose a serious threat to anyone in the area who is unvaccinated or under-vaccinated. The three persistent transmission counties – Rockland, Orange and Sullivan – have alarmingly low vaccination rates.
In Rockland, for example, one county zip code has a polio vaccination rate in children under age 2 of just 37 percent, according to state data. In Orange, a zip code has a vaccination rate of only 31 percent. Vaccination rates across the county of Rockland and Orange are 60 percent and about 59 percent, respectively.
Sullivan County has not provided the state with zip code-level vaccination coverage data. But in an August press release, Nancy McGraw, the county’s director of public health, suggested that some areas of the county have low rates comparable to Rockland and Orange.
“Sullivan County has an overall vaccination rate of 62.33 percent for polio, but there are some parts of the county that have lower vaccination rates, and because polio can spread very easily, it’s important that everyone is vaccinated,” McGraw said at the time. “Public Health offers a safe and proven vaccine for children two months of age or older. We’re working with the state to get adult vaccines. If adults need a vaccine, we encourage: [sic] to contact their healthcare provider.”
Most adults and children in the US have been 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 the occurrence of paralytic disease, and vaccination coverage rates report the percentage of 2-year-olds who followed the recommended vaccination schedule for the first three shots.
Assessing risk
But in low-vaccination areas, such as those in several New York counties, the polio virus — in this case, a revertant virus derived from an oral vaccine used abroad and transmitted among unvaccinated people — can persist. to spread. In the CDC’s new study released today, health officials scoured sewer monitoring data to see where and how extensive that spread is.
They searched for polio virus in 1,076 samples taken between March 9, 2022 and October 11, 2022 from 48 sewers in Rockland and 12 surrounding counties. In total, 89 (about 8 percent) samples from 10 sewers tested positive for the polio virus. Of the 89 samples, 82 were from counties outside of New York City, taken from sewers in Nassau, Orange, Rockland and Sullivan counties. Of those 82 positive samples, 81 were genetically linked to the Rockland County patient, and one, which came from Orange County, did not have enough genetic data to determine the link.
The remaining seven of the 89 positive samples were from New York City, one of which was related to the Rockland case, and five were of insufficient quality to determine linkage. Interestingly, there was one from another poliovirus that was not linked to the Rockland case, suggesting that more than one strain of poliovirus has been introduced into the US.
The strain of polio virus in the Rockland case has been genetically linked to viruses spreading in London and Israel.
The fact that samples from October 4, 5 and 6 tested positive for the polio virus that has already paralyzed one person suggests that others are still at risk in the US.
“[A]Any un or undervaccinated adult or child living or working in Kings, Orange, Queens, Rockland or Sullivan counties should now complete the IPV series,” the study authors concluded.
