There could be hundreds or thousands of undiagnosed cases of polio in just one part of US alone, the BBC reported on Tuesday.
A New York State health official made the comments to the British broadcaster following an announcement last month that an unvaccinated man had been paralyzed by the virus, which affects the spinal cord, in Rockland Country, New York.
His case had reportedly been linked genetically to traces of polio virus found in sewage in London and Jerusalem.
But Dr. Patricia Schnabel Ruppert, health commissioner for Rockland County, voiced fears to the BBC that the case was circulating in her state undetected.
“There isn’t just one case of polio if you see a paralytic case. The incidence of paralytic polio is less than 1 percent,” she told the BBC.
“Most cases are asymptomatic or mildly symptomatic, and those symptoms are often missed,” she continued.
“So, there are hundreds, perhaps even thousands of cases that have occurred in order for us to see a paralytic case… This is a very serious issue for our global world – it’s not just about New York. We all need to make sure all our populations are properly vaccinated,” she said.
Ruppert confirmed to the BBC that scientists are looking at links between the New York paralysis case and traces of poliovirus found in wastewater in London and Jerusalem, after genome sequencing was conducted on samples from the three locations.
The US man who was paralyzed reportedly has a form of so-called “vaccine-derived” polio, that occurs because some countries use a weakened form of the virus in their vaccinations.
In rare cases, this type of the virus can mutate and then be transmitted through to others who are unvaccinated.
Global travel means these cases can crop up in countries which are not used to seeing polio, but where there are pockets of low vaccination, according to the BBC.
Although weaker than the original form of the disease, vaccine-derived polio can still cause serious illness, including paralysis, and can also be life threatening.