Health officials in Columbus, Ohio, are calling the city's mumps outbreak the biggest since the development of the mumps vaccine in the 1940s.
Columbus generally gets an average of one case of mumps a year, but since February, there have been 244 cases reported in an outbreak that began on the Ohio State University campus. Most had already been vaccinated.
The outbreak even pushed officials to open a new clinic, where public health nurses have vaccinated about 150 people, including Sean Hubert, who works in the health care industry.
"You know, if I ended up getting the disease and then passing it to my staff, not only does that feel bad on my part, but then they could certainly pass it to the clients that they serve," Hubert says.
The majority of those infected so far are students or staff at Ohio State. Administrators say they're trying to educate students on ways to limit spreading infection, like frequent hand washing. Still, university officials say there's only so much the school can do.
Graduate student John Vaughn is considering revaccination. "I haven't been back for a booster, but I'm considering it now that I realize that this can pop up even if you've been vaccinated," he says.
As Vaughn notes, vaccinations are not 100 percent effective. The Centers for Disease Control and Prevention say one dose is about 78 percent effective. That increases to 88 percent with a second dose.
Columbus Public Health Commissioner Teresa Long is urging more vaccinations.
"We're in a community outbreak situation," Long says. "That would not have been the recommendation if we did not have that going on here."
Mumps usually brings flu-like symptoms and swollen salivary glands. Most people recover completely after a few weeks, but in rare cases it can have serious, long-term effects, including possible deafness or damage to reproductive organs.
Health officials say it could be several months before this outbreak subsides.
Commissioner Long and the health commissioner of neighboring Franklin County, Susan Tilgner, have sent letters to school leaders asking them to warn parents that children who haven't had the vaccine could have to stay home for 25 days or more if mumps cases cluster in a building, the Columbus Dispatch reported this week.
Jose Rodriguez, a spokesman for Columbus Public Health, told ABC News that 17 cases have turned up in schools, but none of the schools has had more than two cases yet.
"That's when we ... get really concerned," Rodriguez says, "because then it becomes a cluster."