Health officials have confirmed a case of measles in King County.
The man was returning from a trip to Asia and there are concerns he could have exposed others while he was contagious.
He traveled through Sea-Tac Airport and visited the ER waiting room at Harborview on Tuesday.
He was wearing a mask at both locations.
"Most people in our area have immunity to the measles through vaccination, but people should check the exposure locations and their immunization records and call a health care provider promptly if they develop symptoms," the health department said in a statement.
Anyone not immune to measles could show symptoms anytime between August 28 and September 11, according to the department.