Additional measles case in King County and increased measles activity across Washington state

Situation

King County identified an additional measles case in an infant not connected to previous local cases. They were likely exposed during international travel. The infant was not yet vaccinated. Additionally, there has been increased measles activity in eight counties across WA. This includes two recent measles cases within the state with no known source of infection. This raises concern for risk of measles transmission from unknown index cases.

As of April 16, 2026, there have been 37 cases of measles in Washington state in 2026, with three of those identified in King County residents.

Actions requested

Be aware of increasing measles activity in WA and possibility of exposure during international or domestic travel, public locations visited by someone infectious, or to an unknown source.

• Remain vigilant for possible cases of measles.
  • If we see more cases, modified measles can become more common among those with pre-existing immunity. They may not have classic measles signs, such as absent or atypical rash, or symptoms are mild; identification of travel or other exposure risks in the 3 weeks prior should prompt immediate reporting to us at 206-296-4774.
• MMR vaccination remains the most important tool for preventing measles.
  • Most cases are still associated with international travel. Ask patients about upcoming travel plans and offer pre-travel MMR, especially for infants 6-11 months of age.
  • Providers should not discourage families from getting an early second MMR or MMRV dose for their child as long as the minimum interval for the vaccine has been met.
  • At this time, the only recommendation for an early dose of MMR vaccine prior to 12 months of age is for infants traveling internationally or to another U.S. area where it is recommended by Public Health due to an active measles outbreak.
  • MMR recommendations may change locally as the measles situation evolves.
• Ensure you and your facility are prepared for measles BEFORE seeing patients who might be infectious. For more details, go to DOH and CDC.
  • Ensure staff have documented immunity as a condition of employment.
  • Identify patients, both adults and children, without presumptive immunity and vaccinate them if appropriate. Assess at every healthcare visit.
  • Plan for screening incoming patients for symptoms and risk factors before and upon entering the facility.
  • Refer to Measles actions for Healthcare Providers for more details on immediate isolation, notification, testing, and management of patients with suspected measles, and verification of immunity status for all patients.

Be aware of one additional confirmed measles case in a King County infant.

• Secondary cases would most likely occur during April 10, 2026 – April 29, 2026.
• Visit the King County measles website or WA DOH measles website to view the most up to date information about potential public exposure locations. The table below includes locations for this most recent King County case as of today [April 16, 2026].