New York health officials on Thursday reported a polio case in an unvaccinated adult from Rockland County, N.Y. – the first in the U.S. since 2013.

How is an eradicated disease spread?

According to officials, the person likely contracted the virus from an individual who had received an oral polio vaccine, which contains a mild live virus that can replicate and be spread to others. These vaccines are available in other countries, but not in the U.S.

“In the U.S., only the inactivated polio vaccine is used which cannot cause polio, but will protect you,” said Virginia Bieluch, MD, chief of infectious diseases at The Hospital of Central Connecticut.

Although polio was declared eliminated in the U.S. in 1979, children are still routinely vaccinated against polio in four doses – given at the ages of two months; four months; six to 18 months; and four to six years.

According to data from the Centers for Disease Control and Prevention (CDC), approximately 93 percent of two-year-olds have received at least three doses of the polio vaccine.

What is polio?

Polio is viral illness that damages nerves that control muscles, resulting in muscle weakness. Severe cases may result in paralysis and even death.

The virus is highly contagious and is spread through contact with stool from an infected individual or droplets from a sneeze or cough. Symptoms may take as long as 30 days to develop, which also increases the ease of spread.

What are the symptoms?

The symptoms of polio include:

  • Headache.
  • Sudden fever.
  • Sore throat.
  • Neck and back stiffness.
  • Muscle weakness and pain.

Why is getting vaccinated so important?

Before the development of a vaccine in the 1950s, polio was once one of the most feared diseases, with annual outbreaks that resulted in thousands of cases of paralysis, many among children. There is still no cure for polio.

“Most people are too young to remember the fear that this disease caused in the past,” Bieluch said. “It’s very important that everyone be vaccinated against polio to prevent this potentially devastating disease.”