Seattle health officials on Friday warned that a confirmed case of measles involved a Canadian traveler who passed through Seattle–Tacoma International Airport on March 9, prompting exposure guidance for passengers and airport staff. The traveler was in the airport before they were diagnosed and is no longer in King County, officials said. Anyone unsure of their immunity is being urged to check vaccination records and watch for fever or an unexplained rash.
According to Public Health – Seattle & King County, the individual’s vaccination status is unknown, and people who were at SEA on March 9 would most likely develop symptoms between March 16 and March 30. The alert was first reported by KOMO News. County Health Officer Dr. Sandra J. Valenciano has stressed that vaccination is the key step to prevent further spread.
Where exposures may have occurred
Public Health is directing travelers to the county’s measles page for a detailed list of specific airport locations and times tied to the March 9 exposure, along with an interactive exposure map. For information on affected gates, concourses and estimated exposure windows, see King County and follow the posted instructions for people who may have been exposed.
How measles spreads and vaccine guidance
Measles is highly contagious. Symptoms typically appear 7 to 21 days after exposure, and people are contagious from about four days before the rash appears through four days after it starts. The virus can linger in the air for up to two hours, and two doses of the MMR vaccine are about 97% effective, with the CDC outlining expected timing, contagiousness and vaccine protection.
Statewide picture
Local officials note that this case comes amid a broader rise in measles across Washington this year. The Washington State Department of Health dashboard listed 26 confirmed 2026 cases as of Feb. 26, and county posts report additional cases tied to recent outbreaks.
If you were at SEA on March 9
Anyone who was at Sea‑Tac on March 9 and is not immune should contact a healthcare provider before visiting a clinic and should follow the county’s testing and vaccination guidance. High-risk people, including infants, pregnant people and those with weakened immune systems, should reach out to a provider right away or consult the resources on King County’s measles page for local clinics and vaccine locations.
This is at least the second Sea‑Tac exposure this winter; a January exposure was connected to an earlier traveler. Health officials continue to monitor cases and emphasize that vaccination remains the most reliable defense against measles.
