Three more measles cases have been confirmed in Snohomish County after an outbreak began two weeks ago, public health officials said Wednesday.
Earlier this month, three children in Snohomish County tested positive for measles after being exposed to a contagious family visiting from South Carolina, where a massive ongoing outbreak has infected nearly 800 people since October. The Snohomish County kids, who are between 23 months and 9 years old, were not vaccinated and are recovering at home.
Now, three more unvaccinated children have been infected with the highly contagious disease, the Snohomish County Health Department said. Still, the risk to the majority-vaccinated public is low.
Two of the children were diagnosed last week and are siblings of one of the previously infected children, the department said. They were already isolating, and no new exposure sites were linked to those two cases.
But the latest measles case, confirmed Tuesday, may have exposed additional residents.
The child would have been infectious while attending a service at the Slavic Christian Church Awakening in Mukilteo on Jan. 18, exposing anyone in attendance between 2 and 6 p.m., the health department said.
It's not clear whether this week's case was also related to the exposures from South Carolina, or if the child was exposed to a previously undiagnosed case, Snohomish County health officer Dr. James Lewis said.
Part of the uncertainty is because public health teams don't know exactly when the child's symptoms began, Lewis said Thursday. In theory, it's possible the child was exposed at the Mukilteo church when the South Carolina family was there in late December. But it's unusual to see symptoms emerge so long after initial exposure, he said.
It's also possible the child was exposed somewhere else in the last month, from someone infected with measles but who didn't seek medical care and is recovering at home.
Since [the child's family] is not reporting any other sick contacts, we don't really have a good idea of where or when this happened," Lewis said. "That's the reason we think it's likely there are other cases we don't know about."
Public health teams had expected to see more cases after the outbreak was announced. Now, with measles confirmed in multiple households in the county, "the assumption we have to make is there's unrecognized community spread," Lewis said.
“The next two to three weeks could be telling on where this outbreak is going to go," he added in the Wednesday statement. Now is the time to find out your immunization status and get up to date on vaccinations.”
None of the six children with measles in Snohomish County have been hospitalized.
The measles virus can remain in the air for up to two hours after an infectious person leaves the area. The incubation period for measles is typically 10 to 14 days from exposure to onset of symptoms, with a complete range of seven to 21 days.
For people exposed at the Mukilteo church, that would be through Feb. 8. For people who were infected at other Snohomish County exposure sites, they would most likely experience symptoms sometime between the last few weeks and Jan. 29 to Feb. 3.
The measles, mumps and rubella vaccine is safe, highly effective and lasts a lifetime, and two doses offer 97% protection against the virus. The Washington State Department of Health is recommending people living or spending time in Snohomish County get their second dose of MMR 28 days or more after the first dose.
So far this year, the state has confirmed eight measles cases in Snohomish, Kittitas and Clark counties. Of those who have been infected, three were younger than 5, three were between 5 and 17, and two were 18 and older.
In 2025, 12 Washingtonians tested positive for the virus.
Snohomish County also reported Washington's first death of a local child to the flu this season, according to the state department of health.
The child was a “school-age teenager” and died from the flu last week, the Snohomish County health department said.
Flu season is peaking. Ten people in Snohomish County have died from complications related to the flu so far this season, while 222 have been hospitalized. Across the state, 59 residents have died from flu-related complications as of Jan. 17.
The annual flu vaccine is recommended for everyone 6 months and older and can be accessed at local pharmacies and clinics.
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