Public Health – Seattle & King County is warning of a confirmed measles case involving a traveler who passed through Seattle-Tacoma International Airport on Monday, Mar. 9, potentially exposing others to the highly contagious disease.
The individual, a Canadian resident whose vaccination status is unknown, was at the airport between 2 p.m. and 5 p.m. that day and has since left King County, according to health officials.
“If you are not immune to measles or don’t know your vaccination status, and were at the airport on Mar. 9, please visit our measles webpage for specific information about potential areas of exposure within the airport,” officials said.
“We are at a pivotal moment with more measles outbreaks happening throughout the U.S. and abroad,” said Dr. Sandra J. Valenciano, health officer for Public Health – Seattle & King County. “As a result, we may see more cases in King County. But getting vaccinated is a key step in preventing measles from spreading in our community.”
Health officials said measles can spread before an infected person knows they are sick, including before a rash appears. Symptoms typically develop seven to 21 days after exposure, with the most likely onset for this case between Mar. 16 and Mar. 30.
While most people in the region are protected through vaccination and overall risk to the public is considered low, officials advise those who may have been exposed to confirm their vaccination status and watch for symptoms such as fever or rash.
Anyone who develops symptoms should contact a health care provider before visiting a clinic or hospital to avoid potentially spreading the virus, officials said.
Measles is a highly contagious disease that spreads through the air when an infected person coughs or sneezes. It can cause fever, rash, cough, runny nose and red, watery eyes, and in some cases may lead to serious complications including pneumonia or brain inflammation.
Health officials said that if one person has measles, up to nine out of 10 nearby people who are not immune may become infected.
There have been 28 cases of measles in Washington residents so far in 2026.
Location of potential exposure
What to do if you were exposed
Most people in our area have immunity to measles through vaccination, so the risk to the general public is low. However, anyone who may have been exposed should:
- Confirm their measles vaccination status or prior infection
- Ensure they are up to date on recommended MMR vaccinations
- Call a health care provider if they develop an illness with a fever or an unexplained rash
To avoid spreading measles, do not visit a clinic or hospital without calling ahead, and limit contact with others, especially those without known immunity.
Officials emphasized that the measles, mumps and rubella vaccine is safe and effective, with two doses providing about 97 percent protection against the disease.
More information, including specific exposure locations within the airport and vaccination resources, is available at kingcounty.gov/measles.
