A young adult in New York has become the first US resident in nearly a decade to contract polio, state health officials say.
The unnamed patient in Rockland County is said no longer to be contagious, but has developed paralysis from the virus.
Officials say the person was unvaccinated, and was probably exposed to an individual who received a vaccine that contains the weakened live virus.
The last known US case of the highly contagious virus was recorded in 2013.
Once feared across the nation, the disease was largely eradicated by a national vaccination campaign that began in 1955.
Annual cases quickly fell from fewer than 100 in the 1960s to fewer than 10 in the 1970s – and the US was declared polio-free by 1979.
In the decades since, isolated cases of polio infection have been brought into the country by foreign travellers.
Mostly affecting children, the virus causes muscle weakness and paralysis, and in the most serious cases permanent disability and death.
Americans are typically vaccinated with a three- or four-dose regimen that begins at two months old. About 93% of toddlers have received at least three doses of the polio jab, according to vaccination data from the US Centers for Disease Control and Prevention.
But whereas the US and other countries use jabs made with an inactivated version of the virus, some countries orally administer a vaccine that uses the virus in a weakened live form.
That weakened virus may, in rare instances, mutate and risk a fresh outbreak.
Like the patient in Rockland County, the last reported polio case in the US – a seven-month-old child who moved from India to the state of Texas in 2013 – was a vaccine-derived strain.
The news has prompted local officials to schedule vaccination clinics in New York state for Friday and Monday.
“We want shots in the arms of those who need it,” Rockland County health commissioner Dr Patricia Schnabel Ruppert said at a Thursday news conference.
Polio is endemic in Afghanistan and Pakistan, but has also recently been reported in other parts of the world.
Health officials in the UK called on parents last month to vaccinate their children, warning that the virus had been found in London sewage samples.
