State and county health officials in New York announced on Thursday that a case of polio has been discovered in Rockland County.

Why it matters: No polio cases have originated in the U.S. since 1979. The last time the virus was brought into the country via travelers was in 1993, according to the Centers for Disease Control and Prevention.

The big picture: Officials are warning health practitioners to be on the lookout for additional cases, per a press release from the New York State Department of Health and the Rockland County Department of Health.

• Polio is considered to be very contagious, and symptoms can take up to 30 days to appear, per the press release.
• People already vaccinated against the virus have a low risk of contracting it, but health officials are advising those who are unvaccinated or haven't completed their vaccinations to do so.
• Based on the strain of polio that was detected, officials believe the virus likely originated abroad, according to the press release.

What they're saying: "Many of you may be too young to remember polio, but when I was growing up, this disease struck fear in families, including my own," said Ed Day, Rockland County executive, in the release.

• "The fact that it is still around decades after the vaccine was created shows you just how relentless it is," he added. "Do the right thing for your child and the greater good of your community and have your child vaccinated now."

Flashback: Before polio vaccines were available, outbreaks caused more than 15,000 cases of paralysis annually in the U.S. in the 1950s, the CDC noted.