Wyoming’s first reported case of measles in 2026 was confirmed Friday in Fremont County. The adult patient did not have a confirmed vaccination status, according to the Wyoming Department of Health.
Wyoming went 15 years without a confirmed case of measles until last year, when 15 were reported.
The latest announcement comes as cases of the highly contagious disease surge across the U.S. amid worries that falling vaccination rates are undermining community immunity. The neighboring state of Utah is one of America’s 2026 measles hotspots, with 428 cases reported so far this year.
The people most vulnerable to severe impacts of measles are infants, non-immune pregnant women and immunocompromised individuals. More than 90% of confirmed cases in the U.S. since 2025 have infected people who were unvaccinated or had an unknown vaccination status, according to the Centers for Disease Control.
The measles-mumps-rubella vaccine, which is considered highly effective, is typically recommended for children at around 1 year and again between 4-6.
Wyoming residents may have been exposed to the recent measles case at the Walmart Supercenter in Riverton on the evening of April 24, or at a Maverik gas station in Powell the morning of April 25, according to the health department.
“We are asking individuals who were potentially exposed to self-monitor for measles symptoms for 21 days past the exposure date, and consider avoiding crowded public places or high-risk settings such as daycare centers,” Dr. Alexia Harrist, state health officer, said in an announcement.
Wind River Cares and Warm Valley Health Care, clinics that primarily treat residents of the Wind River Reservation, both posted alerts urging clients to be mindful of measles symptoms.
Comeback
Measles was declared eliminated in the U.S. in 2000 — indicating no endemic transmission for 12 months or more. But the infectious disease re-emerged in recent years primarily due to declining vaccination rates and higher public health skepticism. Those trends spawned during the COVID-19 pandemic and have persisted during the second Trump administration.
A vaccination rate of 95% is necessary for community immunity to prevent outbreaks of measles, according to the Centers for Disease Control.
In 2025, Wyoming’s proportion of kindergarten students who had completed the MMR vaccine was 93.6%, according to the CDC. That rate is higher than Colorado, Utah and Montana for the same year.
However, it’s declined overall since 2012-13, when Wyoming’s kindergarten vaccination rate was above 97%. It fell to 90.2% in 2020-21 before inching back up to the current 93.6%.
A case had not been reported in the state since 2010 until July 2025, when the health department confirmed measles in an unvaccinated child from Natrona County. In the following months, the infectious disease also showed up in Niobrara, Carbon, Fremont and Park counties. The majority of cases involved unvaccinated children and adults.
People exposed to measles typically develop symptoms 7 to 21 days after exposure. Symptoms include fever, cough, runny nose, red eyes and a characteristic rash.
The health department stresses the importance of vaccination for containing the illness.
“Measles is one of the most contagious diseases we know, but it is preventable,” Harrist said in an announcement. “Two doses of MMR vaccine are about 97% effective in preventing measles, and we recommend that all Wyoming residents ensure they and their children are up to date on MMR vaccinations.”
Along with being extremely contagious, measles can cause severe complications like pneumonia and brain swelling and can leave lasting impacts on the immune system.
One to three out of every 1,000 children who become infected with measles will die from complications, according to the CDC.
