DES MOINES, Iowa — A mumps epidemic is sweeping across Iowa in the nation's biggest outbreak in at least 17 years, baffling health officials and worrying parents.
As of Thursday, 245 confirmed, probable or suspected cases of mumps had been reported to the Iowa Department of Public Health since the middle of January.
The federal Centers for Disease Control and Prevention said it was the nation's only outbreak, which the CDC defines as five or more cases in a concentrated area.
"We are calling this an epidemic," said Dr. Patricia Quinlisk, Iowa state epidemiologist.
She said mumps had spread across more than a third of the state and did not appear to be confined to any particular part of the population, such as age group.
Iowa has had about five cases of mumps a year in recent years, Quinlisk said, and this is its first large outbreak in nearly 20 years.
"We're trying to figure out why is it happening, why is it happening in Iowa and why is it happening right now," she said. "We don't know."
CDC spokeswoman Lola Russell said the federal agency had no answers.
Quinlisk said one theory was that the infection was brought from England, perhaps by a college student.
The CDC has identified the strain in Iowa as the same one that has caused tens of thousands of mumps cases in a major outbreak in Britain over the last two years.
Mumps is a viral infection of the salivary glands. Symptoms include fever, headache, muscle aches and swelling of the glands close to the jaw.
It can cause serious complications, including meningitis, damage to the testicles and deafness.