Just weeks after the first U.S. case of polio in a decade was detected, the New York City Department of Health and Mental Hygiene reports that there is “likely local circulation of the virus.” On Friday, the department announced that it has detected poliovirus in the city’s wastewater, a sign that the causative agent for the eradicated disease may be making its way around New York.
Health officials have encouraged New Yorkers to get vaccinated. “The risk to New Yorkers is real, but the defense is so simple — get vaccinated against polio,” New York City health commissioner Dr. Ashwin Vasan said on Friday. “With polio circulating in our communities, there is simply nothing more essential than vaccinating our children to protect them from this virus, and if you’re an unvaccinated or incompletely vaccinated adult, please choose now to get the vaccine.” During the pandemic, polio vaccination rates in the city fell as parents delayed visits to the pediatrician. Around 14 percent of kids under 5 in the city have not gotten the full dosage of the vaccine, which is close to 100 percent effective.
In July, an unvaccinated adult in Rockland County, just north of the city, contracted polio. According to local health officials, the person appeared to have a vaccine-derived strain of the virus, suggesting that the person was infected by someone who had received an oral polio vaccine in another country. (Oral polio vaccines, which contain a weakened strain of live virus, haven’t been used in the U.S. since 2000.)
Wastewater epidemiology has been a useful tool during the COVID pandemic, using the presence of the virus in sewage to get a population-level understanding of a local surge before testing confirms a rise in cases. The practice works the same way with polio. “For every one case of paralytic polio identified, hundreds more may be undetected,” said state health commissioner Dr. Mary T. Bassett in a statement.