New York Governor Kathy Hochul declared a disaster emergency on Friday in a bid to accelerate efforts to vaccinate residents against polio after the virus was detected in wastewater samples taken in four counties.
Ms Hochul's executive order followed the discovery of the virus last month in samples from Long Island's Nassau County, bordering the New York City borough of Queens.
Earlier this year, the virus was found in samples from Rockland, Orange and Sullivan counties, all north of the city.
In July, the first confirmed case of polio in the US in nearly a decade turned up in an adult in Rockland County, the state health department said.
“On polio, we simply cannot roll the dice,” Mary Bassett, the state health commissioner, said in a statement.
“If you or your child are unvaccinated or not up to date with vaccinations, the risk of paralytic disease is real.”
Polio can cause irreversible paralysis in some cases, but it can be prevented by a vaccine first made available in 1955. While there is no known cure, three injections of the vaccine provide nearly 100 per cent immunity.
People of all ages are under threat, though the virus primarily affects children aged 3 and younger.
Officials urged unvaccinated adults and minors as young as two months old to get inoculated against the virus, and advised vaccinated people to receive a lifetime booster dose.
Ms Hochul's declaration authorises paramedics, midwives and pharmacists to administer polio vaccinations, among other steps, to accelerate inoculation rates. The order also directs healthcare providers to update the state with data on immunisations.
The state of emergency will stay in effect until October 9. Health official set a goal of getting 90 per cent of residents vaccinated.
The state health department said that people in New York City, Rockland, Orange, Sullivan and Nassau counties are at the highest risk.
Orange County has the lowest vaccination rate of the counties of concern, with less than 59 per cent being immunised, the state health department said.