Updated

Health officials say an outbreak of mumps has particularly hit a community of Marshall Islanders in northwest Arkansas.

The Arkansas Democrat-Gazette (http://bit.ly/2hVVQYf ) reports that Marshallese people accounted for about 60 percent of the state's 2,220 reported cases as of Friday. The outbreak started in August.

The contagious disease causes swelling in the salivary glands and cheeks.

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The Marshall Islands are in the Pacific Ocean. Up to 12,000 Marshallese live in northwest Arkansas.

State health department director Nate Smith says he doesn't know why so many Marshallese people are infected. Officials are investigating if the vaccine is less effective for certain people.

The U.S. Centers for Disease Control and Prevention says Arkansas' outbreak is the largest since about 3,000 people were infected in New York City in 2009 and 2010.