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December 3, 2025

Measles case in visitor to King County: Possible exposures at Seattle-Tacoma International Airport

Public Health – Seattle & King County was notified of a measles case in an adult who traveled on a connecting flight through Seattle-Tacoma International Airport (SEA) on November 11, 2025, and again on November 17, 2025. The individual is an out-of-state traveler and their vaccination status is unknown. If you are not immune to measles or don’t know your vaccination status, and were at the airport on November 11th or November 17th, please visit our measles webpage for specific information about potential areas of exposure within the airport.

Public Health has responded to four other measles cases this year among people who traveled through King County but are not Washington state residents. There have been 12 other cases of measles in Washington state residents this year.

People infected with measles can spread the disease before they know they are infected and before any rash appears. 

The infected person was at Seattle-Tacoma International Airport before being diagnosed with measles. The times listed on our measles webpage include the estimated period when the individual was at each location and two hours after. The measles virus can remain in the air for up to two hours after someone infected with measles leaves the area.

What to do if you were in a location of potential measles exposure 

Most people in our area have immunity to measles through vaccination, so the risk to the general public is low. However, anyone who was in the locations of potential exposure to measles around the times listed on our website should:

  • Find out if you have been vaccinated for measles or have had measles previously. Make sure you are up to date with the recommended number of measles (MMR) vaccinations.  
  • Call a healthcare provider promptly if you develop an illness with fever or with an unexplained rash. To avoid possibly spreading measles to others, do not go to a clinic or hospital without calling first to tell them you want to be checked for measles after an exposure. It is also important to limit contact with others, especially those without known immunity.  

Likely exposure windows:

  • If you were at Seattle - Tacoma International Airport on November 11, 2025, the most likely time for symptoms is November 18 through December 2.
  • If you were at Seattle - Tacoma International Airport on November 17th, the likely time for symptoms is November 24 through December 8.

People who are immuno-compromised may take longer to experience symptoms.  

To help provide information about measles, we’ve created a number of resource materials for schools, workplaces, organizations, healthcare providers, and anyone else in the community to share. Please download and use these resources to help people in your networks learn about measles, how contagious it is, and what they can do to protect themselves and their families.

About measles 

Measles is a highly contagious and potentially severe disease that causes fever, rash, cough, runny nose, and red, watery eyes. If one person has it, up to 9 out of 10 people nearby will become infected if they are not protected. It mainly spreads through the air after a person with measles coughs or sneezes. 

Measles symptoms begin 7 to 21 days after exposure. Measles is contagious from about 4 days before the rash appears through 4 days after the rash appears. People can spread measles before they have the characteristic measles rash. 

Measles can lead to ear infections, diarrhea, pneumonia, and rarely, encephalitis (brain inflammation) or death. 

Complications from measles can happen even in healthy people, but those at highest risk include infants and children under 5 years, adults over 20 years, pregnant people, and people with weakened immune systems from medications or underlying disease. 

If you are in one of these high-risk groups and were exposed to measles at one of these locations, be sure to contact your health care provider to discuss any steps you need to take to protect yourself or loved ones against complications from measles. 

Measles is preventable with the safe and highly effective measles, mumps, and rubella (MMR) vaccine. Two doses of the MMR vaccine are about 97% effective at preventing measles and that protection is long lasting. 

For more information about measles and measles vaccination, including where to get measles vaccinations: kingcounty.gov/measles  

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