The Avengers just finished fighting Thanos, but now a group of people in California that watched “Endgame” may be battling measles.

Orange County officials warned on Wednesday that a woman with measles apparently saw the opening night’s midnight showing of “Avengers: Endgame” in Fullerton before realising she was sick.

As a result, she may have exposed others in the region to the highly contagious disease, according to the Los Angeles Times.

The 20-something patient lives in Placentia and had just returned from a trip to Vietnam, where there has been widespread measles activity, according to Inside Edition.

The woman was unaware she was sick when entered the cinema at 11 pm on Thursday. She didn’t leave until 4 on Friday morning, and she went to the emergency room later that day.

The woman is now under “voluntary isolation” at home.

Orange County Health Care agency spokeswoman Jessica Good told the Orange County Register that the “the exposure risk applies to anyone who was at the theatre during that time period.”

As you might expect, cinema employees are not thrilled that they and others may have been exposed to measles.

“The last place I would ever expect it was at my job. I wasn’t even expecting Orange County,” AMC Fullerton employee Carlee Greer-McNeill told NBC Los Angeles.

She added: “People, if you know you have the measles, please don’t come to a movie theatre, let alone a public place.”