Washington County Works to Contain Potentially Deadly Virus Outbreak

In the first days of 2026, a family visiting from South Carolina moved through shopping centers, schools, and public spaces across King and Snohomish Counties in Washington state. They were infectious with measles. Within weeks, what began as a single exposure event had spiraled into a multi-county outbreak that now stands as a case study in the challenges of containing one of the world's most contagious diseases in an era of declining vaccination rates.

Washington state has confirmed 26 measles cases across four counties in just the first two months of this year—more than double the 12 cases reported in all of 2025 [1]. And the worst, public health officials warn, may be yet to come.

The Epicenter: Snohomish County

Snohomish County, home to roughly 830,000 people north of Seattle, has borne the brunt of Washington's outbreak with 14 confirmed cases—more than half the state's total [2]. The outbreak traces back to late December 2025, when a contagious family from South Carolina visited multiple locations in King and Snohomish Counties between December 27 and January 1 [1].

The first local cases were confirmed in unvaccinated children who had been exposed at the Pathfinder Kindergarten Center and Serene Lake Elementary School in the Mukilteo School District on January 9 [3]. By late January, the virus had spread to a Slavic Christian church community in Mukilteo, where an infected child attended an afternoon service while infectious [4].

"The next two to three weeks could be telling on where this outbreak is going to go," Dr. James Lewis, Snohomish County's health officer, said in late January as the case count climbed [4].

What followed was a massive public health mobilization. Snohomish County health workers made hundreds of contact-tracing calls—roughly 300 after two schools were exposed alone [5]. The state Department of Health laboratory conducted more than 80 measles tests in the first two months of 2026, compared to just nine during the same period in 2025 [5]. Post-exposure MMR vaccinations were offered within 72 hours of known exposures, and Providence healthcare facilities stood up walk-in vaccination clinics [5].

Carrie Parker, the county's assistant director of prevention services and incident commander for the outbreak response, oversaw a team that worked to balance urgency with cultural sensitivity. Health workers provided translated materials and carefully engaged with the affected church community, adjusting their messaging to reduce tension while emphasizing quarantine protocols [5].

"The community and families impacted have been extremely cooperative," health department officials noted in a public statement [4].

A Four-County Problem

While Snohomish County commands the most cases, the outbreak has touched three other counties across the state. Clark County, in southwestern Washington near Portland, has reported eight cases [1]. Stevens County in the northeast has three, and Kittitas County in central Washington has one [1].

Clark County's situation is particularly concerning given its history. In 2018-2019, the county endured a devastating measles outbreak that totaled 73 cases and cost approximately $3.4 million to combat [6]. That outbreak, which spread primarily through churches and households, became a national flashpoint in the debate over vaccine exemptions.

Seven years later, Clark County's vaccination rates have actually declined. During the 2024-25 school year, approximately 83 percent of K-12 students were up to date on their overall vaccinations—the lowest completion rate in five years [7]. The measles vaccination rate among kindergartners dropped to 89.9 percent during the 2023-24 school year, down from 92.1 percent in 2019 [8]. Both figures fall well below the 95 percent threshold needed for herd immunity against measles.

The February 2026 outbreak in Clark County centered on Ridgefield High School, turning a fresh spotlight on the region's vulnerability [7]. Five of the county's confirmed cases involved people who were unvaccinated [9].

Nearly All Cases in Unvaccinated Individuals

The data is stark: of Washington's 26 confirmed cases, 24 involved people who were unvaccinated and two had unknown vaccination status [1]. Not a single confirmed case occurred in someone known to be vaccinated. Nearly 80 percent of the state's cases have been in children, including 16 cases among kids ages 5-17 and four cases in children under five [1].

The pattern mirrors the national picture. Across the United States, 93 percent of confirmed measles cases in the current outbreak cycle have occurred in people who were unvaccinated or did not know their vaccination status [10]. The MMR vaccine remains highly effective: one dose provides 93 percent protection, and two doses are 97 percent effective [1].

"MMR vaccine saves lives and is our best defense against measles," said Dr. Tao Sheng Kwan-Gett, Washington's state health officer [2].

Source: CDC Measles Cases and Outbreaks

Data as of Mar 5, 2026CSV

A National Crisis With Local Consequences

Washington's outbreak exists within a far larger national crisis. As of March 5, 2026, the CDC has confirmed 1,281 measles cases across 31 jurisdictions nationwide [10]. The 2026 total already exceeds the full-year count for 2024 (285 cases) and puts the country on pace to approach or surpass 2025's staggering 2,283 cases—the worst year for measles in the U.S. since the disease was declared eliminated in 2000 [10].

The resurgence is not a blip. After years of minimal transmission—just 13 cases in 2020 and 49 in 2021—cases began climbing through 2022 (121) and 2023 (59), before exploding in 2024 and 2025 [10]. Eighty-nine percent of 2026 cases are outbreak-associated, meaning they are linked to clusters of three or more related infections [10].

Three measles-related deaths have been confirmed nationally: two unvaccinated children in Texas and an unvaccinated adult in New Mexico [11]. A child in Los Angeles County also died from measles-related complications [11]. While measles fatality rates in developed countries remain relatively low—estimated at 1 to 3 per 1,000 infections—the disease carries serious risks. One in five infected children requires hospitalization, one in 20 develops pneumonia, and roughly one in 1,000 develops encephalitis, a potentially devastating brain inflammation [11].

Perhaps most insidiously, measles causes "immune amnesia," effectively wiping out the immune system's memory of previous infections and vaccinations for two to three years after infection, leaving survivors more vulnerable to a range of other diseases [1].

Source: Washington State Department of Health

Data as of Mar 9, 2026CSV

The Summer Threat: World Cup and Travel Season

Public health officials are not just managing the current outbreak—they are bracing for what could be a far more dangerous period this summer. The 2026 FIFA World Cup will bring hundreds of thousands of international visitors to the Puget Sound region for matches in June and July, coinciding with peak summer travel and cruise season [12].

The Pan American Health Organization has specifically raised concerns about measles "in the context of the 2026 FIFA World Cup and other mass gatherings," urging health departments to maintain high alert and robust surveillance [12]. Infectious disease experts point to the convergence of international travel, large crowds, and declining domestic vaccination rates as a recipe for accelerated transmission.

The concern is not theoretical. Genomic sequencing conducted by the Washington Department of Health has already shown that the state's 2026 cases originated from multiple separate introductions from outside the state [1]—meaning the virus is repeatedly being imported by travelers, not just circulating locally.

The Containment Playbook

Washington's response offers a window into the resource-intensive work of measles containment. When a case is identified, health workers must trace every possible contact—a daunting task given that measles is airborne and the virus can linger in a room for up to two hours after an infected person leaves [2]. People can spread measles for days before the telltale rash appears, when symptoms may resemble nothing more than a common cold [12].

In Snohomish County, public health nurse Susan Babcock and her colleagues worked the phones for days, calling families of potentially exposed students and community members [5]. Healthcare facilities were instructed to rapidly isolate anyone presenting with a febrile rash illness, keeping them out of waiting rooms and common areas [13]. Some patients were directed to enter through back doors wearing masks or be seen outside [13].

State and local health departments also pushed aggressive vaccination outreach. Free or low-cost MMR vaccines are available through Washington's Childhood Vaccine Program, Adult Vaccine Program, and Washington Apple Health (Medicaid) [1]. Schools temporarily closed in Everett and Edmonds following exposure incidents [5].

But containment has its limits. With vaccination rates below herd immunity thresholds across multiple communities, each new introduction of the virus has the potential to find fertile ground.

Declining Vaccination Rates: The Root Cause

The fundamental driver of Washington's measles vulnerability—and the nation's—is the steady erosion of vaccination rates. During the 2022-23 school year, four percent of Washington kindergartners received vaccination exemptions; by 2024, that figure had jumped to 4.8 percent [8]. In Clark County, personal belief exemptions have historically been even higher, reaching 7.9 percent of school-age children in the 2017-2018 academic year [14].

These numbers may seem small, but their impact is outsized. Measles requires a vaccination rate of approximately 95 percent for herd immunity to function—a threshold that protects infants too young to be vaccinated, immunocompromised individuals who cannot receive live vaccines, and the small percentage of people for whom the vaccine does not produce full immunity. When vaccination rates slip below that line, as they have in multiple Washington communities, the mathematics of contagion take over.

The decline is not unique to Washington. Nationwide, vaccination exemption rates have been rising, and the CDC has flagged at least 8,500 U.S. schools with vaccination rates low enough to put them at heightened risk of measles outbreaks [15]. The Healthline editorial team has noted that the United States now faces the potential loss of its measles elimination status, which it has held since 2000 [16].

Source: GDELT Project

Data as of Mar 12, 2026CSV

What Comes Next

Washington's health officials are clear-eyed about the challenge ahead. All local health jurisdictions across the state have been advised to prepare for measles cases in their areas [13]. Whole genome sequencing continues on every confirmed case to track transmission chains and identify new introductions [1].

The state's message is consistent and urgent: check your vaccination status, get vaccinated if you are not up to date, and know the symptoms—high fever, cough, runny nose, red watery eyes, and a facial rash that spreads downward, typically appearing 7 to 21 days after exposure [2].

For Snohomish County, the months ahead will test whether hundreds of contact-tracing calls, pop-up vaccination clinics, and community outreach can hold back a virus that is ruthlessly efficient at exploiting gaps in immunity. For the nation, Washington's experience is both a warning and a preview: measles, once vanquished, has found its way back through the door that declining vaccination rates left open.