Recent Mumps Outbreaks

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April 25, 2006

How many cases of mumps usually occur in the US each year?

In the United States , since 2001, an average of 265 mumps cases (range: 231-293) have been reported each year. (See related MMWR article: MMWR Dispatch-Mumps Epidemic-Iowa, 2006 (.pdf) March 30, 2006 [55(13);366-368] )

When did the outbreak in the Midwest start?

The first cases of mumps-like illness were reported from Iowa in December 2005. More cases have been occurring since then in Iowa, and in several other states.

Where did the outbreak in the Midwest start?

The current information indicates that the outbreak may have begun on a college campus. Colleges that have group living, dining, studying, and sports are areas that make disease transmission more likely, and increase the chance of outbreaks. Once started, such outbreaks sometime spread to the community, causing illness in persons who do not attend college. For this reason, CDC recommends that all college students have two doses of measles-mumps-rubella (MMR) vaccine. Studies have suggested that strict enforcement of these recommendations is important for preventing and stopping outbreaks.

Why are people who have been vaccinated getting sick?

One dose of mumps vaccine prevents approximately about 80% of mumps and two doses approximately about 90% of cases. Even though the vaccine is effective, if most persons in a population are vaccinated, most cases in an outbreak would also be expected to be vaccinated. However, if the vaccine hadn't been used, the outbreak would have affected everyone, rather than a small percent of the population.

Does the current vaccine work against the mumps virus that is causing the outbreak?

Yes. The strain of mumps virus in the Midwest is the same as the one that is found in other countries, and that caused a large ongoing outbreak in the United Kingdom (UK) with more than 60,000 cases. In 2005 a small mumps outbreak occurred in the US after a person visited from the UK and mumps vaccine was effective in controlling this outbreak.

Have there been other mumps outbreaks?

Yes. There has been an ongoing mumps outbreak in the United Kingdom (UK). This outbreak was mostly among unvaccinated young adults, 3.3% of them had 2 doses of mumps vaccine, and 30.1% had one dose of mumps vaccine. (See related MMWR article or printable .pdf version.)

There was a mumps outbreak in a camp in New York in 2005 that was believed to have begun after a camp counselor from the UK developed mumps. (See related MMWR article or printable .pdf version.)

Will there be an outbreak in the school I attend/where my child attends?

Many different things affect whether or not an outbreak of mumps might begin in a school, but outbreaks can only begin when there are enough people in an area (school or community) who are not immune from the disease. The best way to prevent a mumps outbreak in a school is to make sure that everyone in that school has had two doses of mumps vaccine (MMR).

What can be done to stop the spread of mumps?

Anyone with mumps should not go back to child care, school or work for 9 days after symptoms begin. People who come in contact with a mumps case should have their immunization status evaluated. Anyone who has not received mumps-containing vaccine (preferably MMR vaccine) should be vaccinated. The local health department or a physician can help determine if a person needs one or two doses of MMR vaccine. Persons who may have been in contact with a mumps case should be educated on the signs and symptoms of mumps disease and should seek medical attention if any of these symptoms begin.

For more, please read the Mumps article.