Moviegoers who went to see "Avengers: Endgame" at a theater in California could have possibly been exposed to measles, health officials said.
The Orange County Health Care agency said a woman who had just returned from a trip abroad was infected with measles when she went to see a midnight showing of the blockbuster hit at the AMC Theater in Fullerton on April 25, according to KNSD. Those who attended the same screening may have been exposed to the disease until around 4 a.m.
Employees at the theater said they were stunned by the announcement.
"The last place I would ever expect it was at my job. I wasn't even expecting Orange County," AMC employee Carlee Greer-McNeill told the station. "People, if you know you have the measles, please don't come to a movie theater, let alone a public place."
The sick female moviegoer, believed to be in her 20s, was placed under quarantine after being diagnosed.
Symptoms of measles usually occur between a week and two weeks after a person is infected, according to the U.S. Centers for Disease Control and Prevention. An individual with the virus can suffer from a high fever, runny nose and watery eyes. Several days after being infected, he or she can also develop a rash that begins on the face and later spreads to the arms, legs and feet.
Orange County health officials encouraged those who think they may have been exposed last week to notify their health providers and check their vaccination history.
The woman's diagnosis is the first in the county. Six other cases have been similarly reported in Los Angeles.
RELATED: Take a look at the treatment, preventative care and vaccinations for measles across the world:
Treatment, preventative care and vaccinations for measles across the world
Treatment, preventative care and vaccinations for measles across the world
A child receives a vaccination against measles by a family physician on April 16, 2018 in the Romanian capital, Bucharest.
Measles still claims young lives in Romania, where nearly 40 children have died in an outbreak that many blame on parents being misled by scare stories that vaccinating them is dangerous. Some 12,000 people have contracted measles since late 2016 in the European Union's second-poorest country, 46 of them died. Among the dead, 39 were children under the age of three who had not been vaccinated, making Romania one of the worst affected countries in the ongoing measles outbreak in Europe. / AFP PHOTO / Daniel MIHAILESCU (Photo credit should read DANIEL MIHAILESCU/AFP/Getty Images)
A family physician prepares a measles vaccine during a consultation on April 16, 2018 in the Romanian capital, Bucharest. - Measles still claims young lives in Romania, where nearly 40 children have died in an outbreak that many blame on parents being misled by scare stories that vaccinating them is dangerous. Some 12,000 people have contracted measles since late 2016 in the European Union's second-poorest country, 46 of them died. Among the dead, 39 were children under the age of three who had not been vaccinated, making Romania one of the worst affected countries in the ongoing measles outbreak in Europe. (Photo by Daniel MIHAILESCU / AFP) (Photo credit should read DANIEL MIHAILESCU/AFP/Getty Images)
A nurse was seen vaccinating school children at her school in Lhokseumawe, August 4, 2018, Aceh, Indonesia. Vaccination Measles-Rubella (MR) for Indonesian school children is part of the Indonesian government's health program to provide physical immunity from two dangerous diseases, Rubella and Measles in Indonesian children. (Photo by Fachrul Reza/NurPhoto via Getty Images)
Artists wearing superhero costumes comfort an elementary student while she receives a German Measles, also known as Rubella, vaccination in Pekanbaru, Riau province on August 1, 2018 as part of the Indonesian governments health program to combat childhood diseases. (Photo by WAHYUDI / AFP) (Photo credit should read WAHYUDI/AFP/Getty Images)
ALEPPO, SYRIA - APRIL 17 : A Syrian child is vaccinated during the measles campaign in Al-Bab district of Aleppo, Syria on April 17, 2018. Kids fled from Eastern Ghouta's Douma after Assad regime forces' suspected chemical attack on April 7, 2018 receive measles vaccine Al-Bab district of Aleppo. (Photo by Omer Alven/Anadolu Agency/Getty Images)
A Venezuelan woman is vaccinated against measles in Cucuta, Colombia, at the international brigde Simon Bolivar on the border with Venezuela, on March 21, 2018. / AFP PHOTO / Schneyder Mendoza (Photo credit should read SCHNEYDER MENDOZA/AFP/Getty Images)
Venezuelan, Yan Manuel, receives a free measles vaccine given by a volunteer, after showing his identity card at the Pacaraima border control, Roraima State, Brazil August 19, 2018. REUTERS/Nacho Doce
A member of the Free Revolutionary Police carries out an inspection on a measles vaccine in the southern Idlib countryside September 17, 2014. Fifteen children died after being vaccinated against measles in northern Syria, resulting in the programme being halted, aid workers said on Wednesday, a tragedy likely to damage trust in health services in opposition-held areas. The Free Revolutionary Police is a newly launched unarmed police movement that works in areas controlled by the Free Syrian Army to solve the day-to-day problems in Idlib, the group said. Picture taken September 17, 2014. REUTERS/Khalil Ashawi (SYRIA - Tags: CIVIL UNREST CONFLICT HEALTH)
A girl receives anti-measles vaccination drops at a health centre in BASECO compound in Tondo, Manila September 3, 2014. Philippine President Benigno Aquino said on September 1, 2014 between 11 to 13 million people in the country are at risk from measles, polio and rubella (German measles), and asked the public to cooperate in eradicating the preventable diseases, during Monday's launch of a mass national vaccination campaign against measles and polio, reported local media. REUTERS/Erik De Castro (PHILIPPINES - Tags: HEALTH SOCIETY)
A vial of measles, mumps and rubella vaccine and an information sheet is seen at Boston Children's Hospital in Boston, Massachusetts February 26, 2015. REUTERS/Brian Snyder (UNITED STATES - Tags: HEALTH)
Rowan Walters, aged four, is held by her mother as she given an MMR injection at the Paediatric Outpatients department at Morriston Hospital in Swansea, south Wales April 6, 2013. Following an increase in the number of confirmed cases of a measles in south Wales, parents in the area were urged to vaccinate their children, and hospitals in the region opened drop-in clinics on Saturday, local media reported. REUTERS/Rebecca Naden (BRITAIN - Tags: SOCIETY HEALTH)
A health worker in Ciudad Juarez at the Mexican border crossing with El Paso, Texas, hands out leaflets to passing motorists and people as part of a measles prevention programme, February 16, 2015. California public health officials have confirmed three more cases of measles in an outbreak that began in late December, bringing to 113 the total number of people believed to have been infected in the state. Health officials in Arizona, where seven cases of measles have been documented, said the outbreak would likely be considered over in that state if no further infections were reported over the weekend. Across the United States, more than 150 people have been diagnosed with measles, many of them linked to an outbreak that authorities believe began when an infected person from out of the country visited Disneyland in late December. REUTERS/Jose Luis Gonzalez (MEXICO - Tags: SOCIETY HEALTH IMMIGRATION)