King County Infant Confirmed as First WA Measles Case of 2025

Public Health – Seattle & King County has confirmed Washington's first measles case of 2025 in an infant from King County, who likely contracted the virus during recent travel abroad. The infant visited several public locations, including the Apple Store and Seattle Children's Hospital, prior to diagnosis, prompting health officials to notify potentially exposed individuals. Measles is highly contagious, with up to 90% of unvaccinated people infected upon exposure, and can remain airborne for up to two hours. Symptoms for those exposed may appear between February 27 and March 18. Health officials are urging residents to check their vaccination status, as vaccination rates in King County are currently below the herd immunity threshold of 95%. The MMR vaccine is approximately 97% effective after two doses, highlighting the importance of vaccination to prevent outbreaks.