The federal Centers for Disease Control and Prevention has identified the mumps strain seen in Iowa as the same one that has caused tens of thousands of cases of the mumps in a major outbreak in Britain over the past two years.

As of Thursday, 245 confirmed, probable or suspected cases of mumps had been reported to the Iowa Department of Public Health since mid-January.

The CDC said it is the nation's only outbreak, which it defines as five or more cases in a concentrated area.

Brought Over From England?

"We are calling this an epidemic," said Iowa state epidemiologist Dr. Patricia Quinlisk, explaining that mumps has spread to more than one-third of the state and does not appear to be confined to certain age groups or other sectors of the population.

Quinlisk said Iowa has had about five cases of mumps a year in recent years, 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. We don't know," she said.

CDC spokeswoman Lola Russell said the federal agency has no answers yet. But Quinlisk said one theory is that the infection was brought over from England -- perhaps by a college student.

"It may have been a college student, since we did see the first activities on college campuses, but we can't prove that," Quinlisk said. The Public Health Department said 23 percent of the 245 reported patients are in college.

The CDC said it is the nation's biggest epidemic of mumps since 269 cases were reported in Douglas County, Kansas, from October 1988 to April 1989.

May Spread to Neighboring States

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.

A mumps vaccine was introduced in 1967. Iowa law requires schoolchildren to be vaccinated against measles and rubella, and the mumps vaccine is included in the same shot. The state's last major outbreak was in 1987, when 476 people were infected.

Of the 245 patients this year, at least 66 percent had had the recommended two-shot vaccination, while 14 percent had received one dose, the Public Health Department said.

"The vaccine is working," Quinlisk said. "The vaccine certainly was made to cover this particular strain, because it's a fairly common strain of mumps." Quinlisk said the vaccine overall is considered about 95 percent effective.

Quinlisk said the mumps outbreak started in eastern Iowa and is spreading statewide and possibly into the neighboring states of Illinois, Minnesota and Nebraska. Those states may have one or two cases, she said.

'Had All the Shots'

When 11-year-old Will Hean of Davenport starting feeling sick in mid-January, his family thought he had a bad case of the flu. But his face and throat swelled and his temperature climbed to 103 Fahrenheit (39 Celsius). His parents took him to the doctor, and he was diagnosed to their surprise with full-blown mumps.

About two weeks later, the Heans' daughter, Kate, 21, came down with the mumps, too.

Both children had gotten the measles, mumps and rubella vaccine, or MMR. So had their other son, 13-year-old Jimmy, who did not get the mumps.

"He had all the shots and everything. You don't think you're going to get the mumps after you've been inoculated," said Will's father, Wayne Hean.