A case of measles was reported at LAX, at Children's Hospital of Orange County

Health officials warned Thursday that people who have been at Los Angeles International Airport and Children's Hospital of Orange County in recent days may have been exposed to measles.

The infected plane was at LAX the day before Thanksgiving, and the infant with measles was in an Orange County hospital after the holiday. It was not immediately clear if it was the same person.

Those most at risk are unvaccinated people who have never had measles before. Children are at high risk of a highly contagious disease.

Others at risk of side effects include pregnant women and people with compromised immune systems.

A person infected with measles arrived at Los Angeles International Airport at 12:35 pm on November 27, on Qatar Airways Flight 739. The flight departs from Doha, the capital of Qatar.

The Los Angeles County Department of Public Health said people who were at LAX's Tom Bradley International Terminal — also known as Terminal B — between 12:30 and 6 p.m. that day may be at risk of contracting measles from exposure to a traveler.

Separately, the Orange County Health Care Agency said a measles patient — an infant returning from international travel — visited the emergency room of Children's Hospital of Orange County three times in recent days: Saturday, between noon and 5 p.m.; Monday between 2 and 10 pm; and on Tuesdays between 5:30 and 9 pm

The exposure comes as measles is on the rise across the country, with 280 cases reported nationally as of Nov. 21, according to the US Centers for Disease Control and Prevention. That compares to 59 measles cases reported in all of 2023.

Of these diseases reported nationally, 41% are among children under the age of five, and 31% of them are among those aged five to 19.

About 9 out of 10 of those measles cases occurred in unvaccinated people, and 112 people were hospitalized. 60 of those hospitalized were under the age of five.

“Before the introduction of the measles vaccine, an estimated 48,000 people were hospitalized and 400–500 people died in the United States each year,” according to the CDC.

The CDC recommends that children receive their first dose of measles vaccine between 12 and 15 months of age, with a second dose at 4 to 6 years of age. Two doses of the vaccine are 97% effective in preventing the disease. The vaccine is known as MMR, which protects not only against mumps but also against mumps and rubella.

“MMR vaccines are very safe. The benefits far outweigh any risks. Side effects are usually mild, such as pain at the injection site,” said the Orange County Health Care Agency.

Infants under 12 months of age who travel abroad should receive vaccinations early, between 6 and 11 months of age, the Orange County Health Care Agency said.

Unvaccinated people are at risk of getting mumps from seven to 21 days after exposure. Measles can spread through the air, and it can stay there or in an area for hours, “even after the infected person has left,” says the LA County Department of Public Health.

“An infected person can spread the disease up to four days before the outbreak of measles and up to four days after the outbreak,” the agency said. “If other people breathe contaminated air or touch an infected area, and then touch their eyes, noses, or mouths, they can become infected.”

Measles symptoms include high fever – possibly over 104 degrees – cough; runny nose; red, watery eyes; and outbreaks, according to the CDC. Serious health problems can occur, especially in children under 5, such as pneumonia – the most common cause of measles death in young children – and inflammation of the brain, which can cause convulsions and lead to deafness or mental retardation.

Of every 1,000 children who get measles, about one in three will die, the CDC says.

There can also be long-term complications from measles, such as SSPE, which stands for subacute sclerosing panencephalitis. SSPE is rare but can occur seven to 10 years after a person recovers from measles, and can lead to a fatal disease of the central nervous system.

The risk of getting SSPE may be higher in those who get measles before age 2, the CDC says.