Mumps is no longer very common in the United States. From year to year, mumps cases can range from roughly a couple hundred to a couple thousand. For example in 2010, there were 2,612 cases reported to CDC, and in 2012, there were 229. Before the U.S. mumps vaccination program started in 1967, about 186,000 cases were reported each year, but the actual number of cases was likely much higher due to underreporting. Since the pre-vaccine era, there has been a more than 99% decrease in mumps cases in the United States.
As of November 5, 2016, 45 states* and the District of Columbia in the U.S. reported mumps infections in 2,879** people to CDC. Six states have reported more than 100 cases this year: AR, IA, IN, IL, MA and OK.
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