A case of polio has been detected in New York, the first known instance of the disease in the US since 2013

• A person in Rockland County, New York, has polio.
• Health officials believe his illness was derived from an oral vaccine no longer used in the US.

A case of polio has been detected in New York, the state health department confirmed on Thursday. It's the first known instance of the disease in the US since 2013.

The case originated in southern Rockland County. Health officials believe the patient was previously given an oral vaccine, which has not been used in the US since 2000 because it has a small chance of causing illness, including paralysis.

While the more widely-used injectable vaccine contains inactivated virus that cannot make people sick, some countries still use oral vaccines containing weakened live virus. In cases of vaccine-derived poliovirus, the weakened virus evolves to behave more like a wild virus, which means it may spread to unvaccinated people.

The vast majority of Americans — more than 92% — get multiple doses of the polio vaccine in childhood, according to the Centers for Disease Control and Prevention. The US uses the injectable vaccine, which cannot cause polio illness or paralysis.

"Based on what we know about this case, and polio in general, the Department of Health strongly recommends that unvaccinated individuals get vaccinated or boosted with the FDA-approved IPV polio vaccine as soon as possible," New York State Health Commissioner Dr. Mary T. Bassett said in a statement.

Most Americans are already vaccinated

The CDC recommends that individuals get four doses of a polio vaccine when they are children: single shots at two months old, four months old, six to 18 months old, and the final dose between 4 and 6 years old.

All 50 states require that children going to public, private, and religious schools, as well as pre-K and day care, get at least three doses of the polio vaccine unless they have a valid medical exemption — resulting in a high rate of vaccine compliance.

"The polio vaccine is safe and effective, protecting against this potentially debilitating disease, and it has been part of the backbone of required, routine childhood immunizations recommended by health officials and public health agencies nationwide," Bassett said.

Polio was nearly eliminated in the US because of the widespread vaccination campaign, and vaccinated individuals have very little to be concerned about today.

In unvaccinated people, polio virus— which tore through the US until the 1950s and 60s — can affect the nervous system and cause muscle weakness, leading to paralysis and even death.

Rockland County is hosting vaccine clinics for community members who have not been vaccinated against polio or have not completed their polio vaccine series. Individuals who believe they have been exposed to polio virus should also get boosted, according to the state health department.

This story is developing. Please check back for updates.