Arkansas seems to have an outbreak of mumps on its hands.
According to the Arkansas Department of Health, more than 400 possible cases have been reported and are under investigation.
The cases currently affect 13 workplaces and three school districts in northwest Arkansas.
The Centers for Disease Control and Prevention says that while mumps isn't common in the U.S., outbreaks still occur.
The number of cases varies from year to year. In 2015 there were 2,612 reported mumps cases, and in 2012 there were 229.
The contagious disease is caused by a virus, and it typically begins with classic cold symptoms, like a fever and headaches. It's known for making salivary glands swell, causing a puffy jaw or cheeks.
In some extreme cases, the virus can lead to swelling of the brain, ovaries or testicles. It can be transmitted through saliva, or mucus from the mouth, nose or throat. So those affected can spread it by sharing items with others or coughing, sneezing or talking.
The good news is that most people recover from the disease in just a few weeks. Two doses of the MMR vaccine, which protects against measles, mumps and rubella, are roughly 88 percent effective in preventing it.
According to the CDC, mumps cases in the U.S. have decreased by more than 99 percent since the pre-vaccine era.
Students who haven't been vaccinated but were exposed to the virus are required to stay home for nearly a month or until the outbreak is over, whichever is longer.