Washington State has confirmed its first measles outbreak of 2023, involving three unvaccinated children in Snohomish County. The children, aged 23 months to 9 years, contracted the disease after exposure to a family from South Carolina who visited various locations in King and Snohomish counties while infectious from December 27, 2025, to January 1, 2026. The Washington State Department of Health (DOH) noted that additional secondary cases could emerge through January 22. Potential exposure sites include Pathfinder Kindergarten Center and Serene Lake Elementary School in Mukilteo, and Swedish Mill Creek Campus in Everett.

Additionally, a case was reported in Kittitas County involving a Central Washington University student who was infectious from January 8 to January 16, 2026. This individual also had ties to the South Carolina family. Public exposure locations include university dining facilities and flight training centers.

DOH emphasizes the importance of vaccination, as measles is highly contagious and can lead to serious health complications. The MMR vaccine is recommended for children and adults who have not been vaccinated. Symptoms of measles typically appear 7 to 21 days after exposure.