Mass exposure at Utah cycling meet linked to new measles cases as U.S. outbreak grows

Four unvaccinated attendees of a Utah High School Cycling League event have tested positive for measles after a mass exposure at Soldier Hollow on Aug. 16, state health officials said, bringing renewed concern as the United States records its largest measles caseload in decades.

The race, held outdoors in Heber City and attended by more than 2,000 people, is linked to the new infections, and the cases have raised the state’s total measles count. Utah health officials are notifying families of participants and urging anyone who attended the Region 6 events to check their MMR (measles, mumps and rubella) vaccination status.

“Measles is highly contagious and spreads easily, even at outdoor events,” Utah State Epidemiologist Leisha Nolen said in a statement. She added that given the number of people who may have been exposed, attendees and participants of upcoming league events should confirm their vaccination records and seek guidance from local health departments if symptoms develop.

Measles is caused by a virus that typically begins with flu-like symptoms and fever, followed by a rash that spreads from the face downward. Patients are contagious from four days before the rash appears through four days afterward. The virus spreads through respiratory droplets and can linger in the air, so people who are not vaccinated have about a 90 percent chance of becoming infected after exposure.

Nationwide, the U.S. has recorded 1,454 measles cases in 2025, the highest annual total since the disease was declared eliminated in 2000. Three deaths have been reported this year, including one adult in Colorado and two children in Texas, officials said. Health authorities have confirmed 266 cases within the last two months alone.

Public health officials point to declining vaccination coverage as a key factor in the resurgence. The Centers for Disease Control and Prevention reports that national coverage for the two-dose MMR series among kindergartners fell to 92 percent for the 2024–25 school year, below the 95 percent threshold generally considered necessary for herd immunity. Utah’s MMR coverage is estimated at about 90 percent, and statewide kindergarten immunization rates have dropped from an average above 85 percent in 2014–15 to roughly 78 percent in 2024–25, according to state surveys.

The two-dose MMR vaccine is about 97 percent effective at preventing measles. Before the vaccine’s widespread use, the U.S. saw thousands of hospitalizations and hundreds of deaths from measles annually. Medical experts say vaccination remains the most effective way to prevent infection and community spread.

Health departments are also working to contain cases through contact tracing and by alerting health care providers and the public about potential exposure windows. People who were at the Soldier Hollow event and who are not up to date on MMR vaccination are being advised to contact their health providers or local health department. Unvaccinated individuals exposed to measles face a high risk of infection; in some situations, health authorities may offer post-exposure prophylaxis.

Public health officials and analysts have also cited a resurgence of vaccine skepticism, amplified by prominent public figures, as a contributor to falling vaccination rates. Robert F. Kennedy Jr., who has been a vocal vaccine skeptic, has in the past repeated widely discredited claims linking the MMR vaccine to autism and has promoted alternative or supplemental remedies, including cod liver oil and vitamin A. Medical guidelines note that vitamin A can be used as supportive therapy in populations with deficiency and may reduce complications, but it is not a cure for measles and can be toxic at high doses. Last spring, clinicians in Texas reported cases of severe vitamin A toxicity among children treated during measles outbreaks.

Health officials emphasize that measles can lead to severe complications, including pneumonia, seizures, encephalitis, permanent brain damage and death, particularly in infants and immunocompromised people. They recommend that adults check their vaccination records for the two-dose MMR series and that parents ensure children receive the recommended doses: one at 12–15 months and a second at 4–6 years, or as directed by health providers for catch-up schedules.

As investigations continue, state and local health agencies said they would provide updated exposure notices and vaccination clinics as needed. Officials urged anyone who develops fever or rash after potential exposure to seek medical care promptly and to notify health providers of possible measles exposure before arrival to prevent further transmission in clinical settings.