New York Gov. Kathy Hochul declared a state of emergency after wastewater testing found evidence of polio in Nassau County.
Polio had recently been detected in Rockland, Orange and Sullivan counties.
So far, only one identified case of polio has been detected. An unvaccinated man in Rockland County suffered from paralysis of the legs after contracting polio.
Hochul's declaration allows more health care professionals to administer polio vaccines, including nurses, midwives, paramedics and pharmacists.
Health officials are urging all unvaccinated New Yorkers to get immunized right away.
"On polio, we simply cannot roll the dice," State Health Commissioner Dr. Mary T. Bassett said. "If you or your child are unvaccinated or not up to date with vaccinations, the risk of paralytic disease is real. I urge New Yorkers to not accept any risk at all."
According to the Centers for Disease Control, about 1 in 100 individuals will develop severe disease after contracting polio, including permanent paralysis, which could turn fatal.