(CNN) A University of California Los Angeles employee who contracted measles ate at a campus food court twice last week while believed to be contagious, according to campus officials who are now warning of potential exposure to the virus.

The employee's case is the 12th confirmed case of measles in Los Angeles County this year, according to a statement from the county's Department of Public Health, which is investigating. It comes amid the largest outbreak in the United States since the disease was declared eliminated in 2000.

The employee ate lunch on July 2 and July 3 at a fast food restaurant in the UCLA Court of Sciences Student Center, the university said in a statement. The school and public health department have asked anyone who was in the center, known as the Bomb Shelter, between 9 a.m. and 11:30 a.m. on those days to see a healthcare professional to determine their immunity to measles.

Anyone who may have been at that location risks developing measles within 21 days of the exposure, an advisory from the health department issued Tuesday said.

"Campus epidemiologists and top health experts have been working closely with the county public health department to ensure that all who might be affected receive notifications and proper care," Michael Beck, the university's administrative vice chancellor said in a statement. "Upon learning of the situation, UCLA identified and notified employees who may have come into contact or who may have otherwise been exposed."

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