The Seattle and King County Public Health Department reports a passenger with contagious measles made a stop at Seattle-Tacoma International Airport on Jan. 18.

Measles is highly contagious, although most people are immune to the disease because of vaccinations. Spokesman James Apa says the health department warning is for people who are unsure of their immunity and develop an illness with fever or an unexplained rash before Feb. 9.

Measles, also known as rubeola, causes fever, rash, cough, and red, watery eyes.

People at highest risk include those who are unvaccinated, as well as pregnant women, infants under six months and those with weakened immune systems.

The contagious traveler flew from Amsterdam to Portland, Ore., through a connecting flight in Seattle. People who flew on Jan. 18 through a south or north gate or took an airport train may have been exposed. After arriving in Oregon, the traveler received medical treatment and public health authorities were notified.