DELAWARE, Ohio (WTVN) -- There is concern that dozens of people in Delaware County may have been exposed to the measles.

A person with a suspected case of the highly contagious illness visited the emergency room at Grady Memorial Hospital in Delaware on Sunday, April 27 between 10:30 a.m. and 2:30 p.m. and again from 11 p.m. to 4 a.m. The person also visited the Marion Area Physicians, formerly known as Smith Clinic, on Thursday from 3:30 to 7 p.m.

"Our concern is that some of the people who might have been in those rooms at the same time have now possibly been exposed and if they are unvaccinated for the measles, mumps, and rubella then they could become ill," said Sheila Hiddleson, Delaware County Health Commissioner.

Getting an MMR vaccine within 72 hours of exposure should provide immunity from the disease. That means for those at the clinic they'll need a shot before Sunday. The Delaware General Health District will be opening a special walk-in clinic on Sunday from 1:00 to 3:00 p.m. for only those unvaccinated persons exposed at the clinic.

Hiddleson says less than 50 people were potentially exposed at the clinic, but there's no accurate count at the hospital.

"We do not know how many people were in the emergency room during those hours," she said.

More than 90 percent of people who are not immune will get measles if they are exposed to the virus. Two doses of MMR vaccine provide full protection against measles to 99 out of every 100 person vaccinated. 

Symptoms begin about 10-12 days after a person is exposed and include fever followed by a blotchy rash, cough, runny nose, red watery eyes, achiness and tiny white spots with bluish-white centers found inside the mouth. It's possible that someone who now has the illness doesn't even know it yet.

Anyone born before 1987 wouldn't have been required to get a second dose of MMR vaccine for school. Those born before 1957 likely developed immunity from exposure to measles and mumps.

The measles cases are linked to Knox County where several people went on a missions trip to the Philippines and were exposed to the disease there.