The number of mumps cases has grown by two since the end of last week, for a total of 23 in the city of Columbus.
The new numbers include one more person sent to the hospital, for a total of three.
There is a growing concern that those numbers could increase in the coming days and weeks.
But doctors say if and when new cases pop up, they will be ready.
The university and city health department are putting out an awareness blitz to educate students and the general public about mumps. Volunteers are putting up flyers with basic hygiene and infection control tips in dorms, frat and sorority houses and off-campus housing.
For some students walking to class on the first day back from spring break, mumps were not even on their minds.
"I'm really confused," said Jamie Van Voorhis, a sophomore. "I'm not sure what it is, if I should be worried or not."
"I think it's pretty ridiculous," said Ben Schumann, another sophomore. "There are vaccines for that, people should be taking those."
But even a small percentage of people like Schumann who got their vaccines are still susceptible to the mumps virus.
"We got at least one case here today, but they're not coming in large numbers," said Dr. Mary Lynn Kiacz, the medical director for Student Life Services on the Ohio State campus.
"If they do come in here, we mask the students, we put them in an isolation room, we do the evaluation and the lab testing, then if we do suspect they have mumps, we send them home, recommending they stay isolated for five days," she added.
Students showing symptoms of mumps are given 'Get Well, Stay Well' bags at the campus health center.
The bags come with a lot of information. They also come with hand sanitizer, temperature strips and masks to wear if they go out in public.
Dr. Kiacz says the clinic could still be seeing cases for weeks.
"There is this long incubation period with mumps, so we still don't know what's going to be coming," she said.
City health officials say finding the source is a puzzle that may not be solved.
"We have several cases, some of which presented with symptoms on the same day, but we don't have the person who may have started this outbreak," said Mysheika Williams Roberts, as assistant health commissioner with the Columbus Department of Health.
Students are getting the message, and hoping for the best.
"It's kind of weird, mumps is something you don't hear about a lot, I guess," said Freshman Taylor Woodhouse. "I just hope I don't get it."
Dr. Kiacz says the big challenge is getting infected students to stay isolated and wear their masks in public.
She says a big effort going on now is to get professors on the same page, so that if students have to miss class, they'll still be able to get their notes.
Health officials are urging people to make sure all their family members have their MMR - the measles, mumps and rubella vaccines.
They also emphasize that everyone should always follow basic hygiene rules like washing hands, covering sneezes and coughs and not sharing glasses or eating utensils.