Health experts scramble to contain mumps cases

Local, state and federal health experts are urgently trying to contain a large mumps outbreak raging across Iowa that has spread to at least eight other Midwestern states.

At least 515 mumps cases have been reported in Iowa this year, far outpacing the five cases the state usually sees in a year and the 200 to 300 that typically occur nationally. The epidemic, the largest since a 1988 outbreak in Kansas, shows no sign of slowing, with at least 100 more cases in Nebraska, Kansas, Minnesota, Wisconsin, Indiana, Michigan, Missouri and Illinois.

Among other steps, the effort to stem the outbreak has led investigators to hunt down passengers on a March flight to Washington, D.C., that carried a woman who later developed mumps, and to vaccinate more than a dozen people she visited on Capitol Hill.

As health officials work to break the chain of transmission of the viral infection, disease detectives are trying to puzzle out what is causing it. Cases appear concentrated among young, otherwise healthy adults.

"Why Iowa and why now? We really don't know," said William Bellini of the federal Centers for Disease Control and Prevention (CDC) in Atlanta. "There are a lot of unknowns."

Among them: Does the mumps vaccine fail to "take" in more people than had been thought? Does its protection wane? Is the virus causing this outbreak less susceptible to the vaccine for some reason, or more infectious?

The outbreak has underscored that old infectious diseases that most people rarely think about — and doctors don't often encounter — can suddenly re-emerge.

The mumps virus is spread by coughing and sneezing. The most common symptoms are fever, headache and swollen salivary glands under the jaw. But the disease can lead to more severe problems, such as hearing loss, meningitis and fertility-diminishing swollen testicles.

No deaths have been reported from the current epidemic.

To try to keep the outbreak from widening further, the CDC announced Wednesday that officials are trying to track down 222 airline passengers who sat near two people from Iowa who developed mumps after traveling on nine flights between March 26 and April 2.

In the states that already have cases, officials are alerting the public to the symptoms in hopes that anyone who has been infected can be identified quickly and isolated. They also are trying to identify and inoculate unvaccinated adults.

Officials speculate that the epidemic might have been sparked by someone from Britain, which has been experiencing a large mumps outbreak for several years. Last summer, a much smaller outbreak at a summer camp in New York was started by an unvaccinated British counselor.

Experts hope the relatively high U.S. vaccination rates will contain the outbreak. The tens of thousands of cases in Britain have been blamed on problems with that country's vaccination program, and concerns among some parents that childhood vaccines may increase the risk of autism, which left a significant proportion of the population unvaccinated.

"The United States, fortunately, generally has good vaccine coverage," said Stanley Plotkin, an infectious-disease expert from the University of Pennsylvania.

The mumps vaccine is believed to be about 95 percent effective, meaning that among 100 fully vaccinated people, five would still be vulnerable, enough to allow an outbreak to occur.

But the size of the current episode has experts wondering whether the vaccine is actually less effective than that, and whether the immunity wanes over time. About 68 percent of the cases have occurred among people who received the two recommended doses of vaccine as part of their routine childhood immunizations.

Material from The Associated Press is included in this report