Los Angeles County health officials warned Monday that people who were at Los Angeles International Airport earlier this month may have been exposed to measles.

Three people with measles were in LAX terminals 4 and 5 on Wednesday between 6:50 a.m. and noon. They are not L.A. County residents, officials said.

Anyone who was in those terminals during that time may be at risk of developing measles within the next 21 days, according to public health officials. They advised that people check if they are immunized against measles and to monitor themselves for symptoms.

There is no known risk of contracting measles at LAX currently, officials said.

The warning is one of at least six that county officials have issued this year about a possible measles exposure at LAX, amid outbreaks in several other countries. Nationwide, there have been 1,276 cases this year, compared with 375 cases last year.

Measles is spread through the air. The virus can linger in a room for up to two hours after an infected person leaves, waiting to infect someone else, experts say.

“For those who are not protected, measles is a highly contagious and potentially severe disease that initially causes fever, cough, red, watery eyes, and, finally, a rash,” said L.A. County Health Officer Dr. Muntu Davis in a statement.