The Wyoming Department of Health (WDH) announced on Dec. 19 that it’s confirmed a case of measles in a Park County resident. The adult was fully vaccinated but had extensive exposure to measles while abroad and developed a mild illness, the department says.

While it is rare for immunized individuals to develop measles infection, it can occur and typically results in milder illness compared to unvaccinated individuals, the department says. Of the 1,958 measles cases reported in the U.S. to date in 2025, 93% have been unvaccinated.

The Department of Health is notifying all identified individuals potentially exposed to measles in Park County. It says anyone who visited the Cody Albertsons between 1:30-4 p.m. on Dec. 15 or from 2:30-5 p.m. on Dec. 17 or who visited the Cody Walmart between 2:30 and 5 p.m. on Dec. 18 may have been exposed, as the virus can remain in the air for up to two hours after an infectious individual leaves an area.

Measles is highly contagious and can cause serious illness — including pneumonia, encephalitis, hospitalization, and death — but public health experts say the measles, mumps, and rubella (MMR) vaccine provides highly effective and long-lasting protection. The Wyoming Department of Health recommends all Wyoming residents ensure they and their children are up to date on MMR vaccines. The vaccines are widely available through providers’ offices, pharmacies, and public health nursing offices. 

For more information on measles, including guidance on what to do if you were exposed, visit tinyurl.com/27x92bxk.

There have been 15 cases of measles reported in Wyoming so far this year.