Mumps Cases and Outbreaks

As of April 1, 2021, a total of 11 mumps cases were reported by 7 states.

Reported US Mumps Cases by State by Year*

Mumps Reported Cases-2021

Reported Mumps Cases by Year — United States, 2000-2021*

*2021 map represents cases reported to CDC as of April 1, 2021; 2020 and 2021 case counts are preliminary and subject to change.

Mumps Cases

Before mumps vaccine was available in the United States, most children got mumps by the time they reached adolescence. Reported cases decreased by more than 99% after both the mumps vaccination program started in the U.S. in 1967 and children regularly received two doses of MMR vaccine. Cases decreased from 152,209 in 1968 to 231 in 2003. However, mumps cases and outbreaks reported in the United States have increased since 2006. Most of these cases were in young adults and people who were vaccinated.

Large outbreaks have happened in settings where people have intense or frequent close contact, like college campuses, close-knit communities, and large gatherings.

Outbreaks

Mumps outbreaks can occur in U.S. communities of people who previously had 1 or 2 doses of MMR vaccine. Large outbreaks are more likely to occur in close-contact settings. High vaccination coverage helps limit the size, duration, and spread of mumps outbreaks.

  • In 2020, mumps cases decreased compared with the previous six years, possibly due to social distancing and other COVID-19 prevention measures. However, mumps continued to circulate across the U.S. despite these measures. From April 1, 2020 to December 31, 2020, 32 health departments reported 142 mumps cases.
  • From 2015 to 2019, the U.S. saw a range of different mumps outbreak settings and sizes. Cases started to increase in late 2015.
    • From January 2016 to June 2017, health departments reported 150 outbreaks (9,200 cases). Outbreaks occurred in households, schools, universities, athletics teams and facilities, church groups, workplaces, and as a result of large parties and events.
    • The largest outbreak occurred in a close-knit community in northwest Arkansasexternal icon that resulted in nearly 3,000 cases.
    • Two large outbreaks in Iowa and Illinois each involved several hundred university students.
    • About half of the outbreaks involved more than 10 cases.
    • From September 1, 2018 to August 22, 2019, 19 state health departments reported 898 mumps cases in adult migrants detained in 57 detention facilities.
  • From 2009 to 2010, two large outbreaks occurred.
    • One outbreak involved over 3,000 people and mostly affected students who were part of a close-knit religious community in New York Cityexternal icon and attended schools where they participated in close-contact activities. The outbreak started when an infected student 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 Guamexternal icon.
  • In 2006, the United States experienced a multi-state mumps outbreak involving more than 6,500 reported cases. This resurgence mostly affected Midwest college-aged students on many different Midwestern college campusesexternal icon.
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