Here’s how this year’s closely related polio outbreaks in New York state, London, and greater Jerusalem might have started. A child in Afghanistan or Pakistan received two drops of Albert Sabin’s oral polio vaccine (OPV), which contains a weakened, live virus, in December 2021 or so. Soon after, when the child was still shedding some virus in their stool, their family traveled to the United Kingdom, where the vaccine virus found fertile ground in an undervaccinated Orthodox Jewish community in London and began to circulate person to person. Somewhere along the way, it also began to change, picking up mutations that can turn the vaccine virus into one that, in rare instances, can paralyze.
That virus then jumped to Israel and to an Orthodox Jewish community in Rockland County, northwest of New York City, says Nicholas Grassly, an epidemiologist at Imperial College London and member of the U.K. National Authority for the Containment of Poliovirus. He reconstructed the “plausible” scenario based on the epidemiological timeline and viral sequences detected in sewage. In Rockland County, an unvaccinated young man in the Orthodox community sought care for weakness in his legs in June—the first U.S. polio case in a decade.
The outbreak, which is continuing, underscores the risks facing unvaccinated and undervaccinated people even in wealthy economies. All three countries have ramped up vaccinations, and on 9 September, New York Governor Kathy Hochul declared a state of emergency in an attempt to curb the outbreak.
