Story highlights In Clark County, Nevada, 4 of 9 measles cases linked to Emeril's New Orleans Fish House

CDC: 154 measles cases discovered in United States from January 1 to February 20

(CNN) Four cases of measles have been linked to a restaurant at the MGM Grand Hotel & Casino in Las Vegas, the Southern Nevada Health District reported Friday.

A patron and two staff members of Emeril's New Orleans Fish House probably contracted measles from a contagious staff member, the health agency said Friday in a press release, bringing to nine the total number of people diagnosed with measles this year in Clark County, Nevada.

An infant too young to have received the immunization may have transmitted measles to the initial Emeril's staff member, the health district said.

A record number of U.S. measles cases -- 644 cases from 27 states -- were reported in 2014. That's the greatest number since measles elimination was documented in the United States in 2000.

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