It was a single case of illness that, according to Brittany Strickland, caused her to fear death. For the first time in nine years, a case of polio was detected in the United States in July – and the 33-year-old from Pomona in Rockland County, which is almost 50 kilometers north of Manhattan in New York State, had not been vaccinated against polio as a child. “My mother was anti-vaccination,” says Strickland.

Polio, or poliomyelitis for short, was once common and feared around the world. Thousands of children died in waves of infection or were left permanently paralyzed until a vaccine was found in the 1950s. The infectious disease is now considered eradicated in most regions of the world. Only in countries like Afghanistan or Pakistan does polio still occur.

The virologist John Dennehy from City University in New York also assumed until recently that polio was “a virus on the way to extinction”. But then the case was reported in Pomona in July. Since then, the virus has also been found in sewage samples in Rockland and a neighboring county, as well as in metropolitan New York – so it appears to be spreading.

The wild type of the virus is probably not causing problems in New York. The oral vaccination against polio used in the USA until the year 2000 protects vaccinated people well against infection, but can lead to infection in other people via faeces in the wastewater contaminated with vaccine viruses. Although the virus variant that occurs is weaker than wild poliovirus, it can still cause serious illness and paralysis in unvaccinated people.

The infected person in Pomona was a young man who had not been vaccinated against polio. The New York City Health Department said it was a “worrying but not surprising” case. She called on all people who are not yet vaccinated to get vaccinated quickly. Vaccinations are even free in Rockland.

While the vaccination rate for two-year-old children is 92 percent nationwide, according to the US health authority CDC, only 79 percent are vaccinated in the state of New York. In Rockland, at 60 percent, just over every second toddler has received a polio vaccine.

Local media reported that the infected man, a man in his 20s, was from an Orthodox Jewish community in Rockland. Orthodox Jews are particularly skeptical about vaccinations – and are heavily represented in Rockland County. More than a dozen rabbis recently issued an open letter urging their parishioners to get vaccinated against polio.

Shoshana Bernstein, herself an orthodox Jew, also educates the communities about vaccinations. She hopes that the older members of the congregation will help. You could still remember polio outbreaks in the 1950s and convince younger people to get vaccinated, says Bernstein. “In a community where family and elders are valued, that has an impact.”

Whether the Pomona case is part of a larger outbreak is still unclear. Virologist Dennehy fears that this is only the “tip of the iceberg”. Only some of those infected will show symptoms and only a fraction will develop paralytic poliomyelitis with the typical paralysis. If the disease spreads, however, more severe cases would also occur.

Strickland has now been vaccinated against polio. “One thinks that nothing like that will happen here. And then some people don’t get vaccinated – and now we’re in this situation.”