Utah Measles Outbreak Reaches 680 Cases After Year-Long Battle, Threatens U.S. Measles-Free Status

A year-long measles outbreak in Utah has infected over 680 people across 22 counties, threatening the U.S.'s measles-free status. The spread is fueled by declining vaccination rates, with 12.8% of kindergarteners statewide unvaccinated, well below the 95% needed for herd immunity. Health officials are concerned about a fall surge, while international experts will meet in November to review the U.S.'s status as the national case count exceeds 2,100.

Utah measles outbreak scope

• ▪State epidemiologist Leisha Nolen is concerned that the start of school and colder weather could cause measles to surge again.
• ▪The measles outbreak has spread to 22 of Utah's 29 counties.
• ▪An exposure at a state high school wrestling championship in February sparked at least 46 measles cases among attendees.
• ▪More than 680 people in Utah have gotten sick with measles since an outbreak began on June 20, 2025.

Measles disease characteristics

• ▪A rare but fatal degenerative brain disease can develop approximately a decade after a measles infection.
• ▪Measles is one of the most contagious diseases and can cause dangerous complications like pneumonia, brain swelling, or death.
• ▪The measles vaccine is safe and provides 97% protection against the disease after two doses.

Declining vaccination rates

• ▪In Utah's "tricounty" health region of Daggett, Duchesne and Uintah counties, more than 16% of kindergarteners were missing their measles vaccines.
• ▪A 95% vaccination rate is required to prevent measles outbreaks in a community.
• ▪In the last school year, 12.8% of Utah's kindergarteners were missing their measles vaccine, putting the state below the 95% target for outbreak prevention.

TriCounty health response

• ▪As a mitigation measure during the outbreak, unvaccinated students were excluded from in-person school and sick individuals were told to isolate.
• ▪The TriCounty Health Department worked to be seen as a helpful community resource rather than a policing agency to build trust.
• ▪Dr. Ellie Brownstein of the American Academy of Pediatrics opposed a Utah bill that would have made it easier to get school vaccine waivers.

U.S. measles-free status threat

• ▪As of June 18, the national measles case count in the U.S. was 2,104.
• ▪A country is considered to have eliminated measles when it has stopped continuous, local transmission for at least one year.
• ▪The prolonged measles outbreak in Utah could cause the United States to lose its measles-free designation.
• ▪International health experts will meet in November to decide if the U.S. and Mexico have lost their measles elimination status.

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