As of Nov. 5, 2016, 45 states and the District of Columbia reported mumps infections in 2,879 people. This year's mumps outbreak is the highest it has been since 2006, according to CDC data.
Six states have reported more than 100 mumps cases this year, with Arkansas now investigating 1,514 cases.
The CDC's data shows that while 2016 has seen more mumps cases than any other year in the last decade, it does not rival the numbers in 2006, when there were more than 6,000 reported cases. So far in 2016, the number of cases has been inching towards 3,000. The only other comparable year in the last 10 years is 2010, which saw 2,612 reported cases. The country's record low for mumps cases in the last decade was 2012, with only 229 reported cases.
The measles-mumps-rubella vaccine prevents most, but not all, cases of mumps. A major factor contributing to mumps outbreaks is being in a crowded environment with a person who is infected with the mumps, according to the CDC.