Mumps Cases and Outbreaks

Mumps Cases

Mumps is no longer very common in the United States. Each year, on average, a few hundred people in the U.S. are reported to have the disease. Before the U.S. mumps vaccination program started in 1967, about 186,000 cases were reported each year. Since the pre-vaccine era, there has been a more than 99% decrease in mumps cases in the United States.

Mumps Outbreaks

2014 Mumps Cases and Outbreaks

From January 1 to July 8, 2014, 965 people in the United States have been reported to have mumps. Outbreaks in at least four U.S. universities have contributed to these cases:

In 2013, 438 people from 39 states in the U.S. were reported to have mumps.

In some years, there are more cases of mumps than usual because of outbreaks. Mumps outbreaks can occur any time of year but often occur in winter and spring. A major factor contributing to outbreaks is being in a crowded environment, such as attending the same class, playing on the same sports team, or living in a dormitory with a person who has mumps.

Although the measles-mumps-rubella (MMR) vaccine is very effective, protection against mumps is not complete. Two doses of measles-mumps-rubella (MMR) vaccine are 88% effective at protecting against mumps; one dose is 78% effective. Outbreaks can still occur in highly vaccinated U.S. communities, particularly in close-contact settings. In recent years, outbreaks have occurred in schools, colleges, and camps. However, high vaccination coverage helps limit the size, duration, and spread of mumps outbreaks.

2014 Mumps Outbreaks

In 2014, mumps outbreaks have been reported in at least four U.S. universities:

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Past Mumps Outbreaks

In 2011-2013, there were several smaller mumps outbreaks reported on college campuses in California, Virginia, and Maryland. However, these all had limited spread, and national case counts for these years were at usual levels (several hundred cases per year).
In 2009- 2010, two large outbreaks occurred.
- One outbreak involved about 3,000 people and mostly affected high school-aged students who were part of an insular religious community in New York City and attended schools in which they had very close contact. The index case-patient was an 11-year-old member of the religious community who had returned from the United Kingdom where a large mumps outbreak was occurring.
- The second outbreak involved about 500 people, mostly school-aged children, in the U.S. Territory of Guam.
In 2007-2008, the number of reported cases returned to usual levels (several hundred cases per year), and outbreaks involved fewer than 20 cases.
In 2006, the United States experienced a multi-state mumps outbreak involving more than 6,500 reported cases. This resurgence predominantly affected college-aged students living in the Midwest, with outbreaks occurring on many different Midwestern college campuses.

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