The Colorado Department of Public Health and Environment, the Archuleta County Public Health Department (ACPHD), and the Silver Thread Public Health District have confirmed a case of measles in an Archuleta County adult resident. The person’s vaccination history is unknown at present. The current evidence shows that the case is likely not linked to the cases in Pueblo or Denver.
The person sought care at a medical clinic in their community on Monday, March 31, and was contagious from March 26 – April 3, 2025.
“This case does not appear to be linked to the other cases reported in Colorado and the individual did not travel outside of Colorado, which leaves open the possibility of community transmission,” said Dr. Rachel Herlihy, state epidemiologist and deputy chief medical officer at the Colorado Department of Public Health and Environment. “We urge Coloradans to monitor for symptoms if they may have been exposed, and to make sure they are up to date on their MMR vaccinations.”
Colorado has a total of three confirmed measles cases in 2025. The confirmed cases have been in Pueblo, Denver, and Archuleta counties.
Measles is highly contagious and often severe, but it is a preventable disease. The MMR vaccine remains the best protection against measles. Two doses of MMR vaccine are about 97% effective in preventing measles. Vaccination is the best way to protect yourself, your family, and your community.
Based on available information, anyone who was in the following locations during the dates and times listed may have been exposed to measles and should monitor for symptoms for 21 days after exposure and consider avoiding public gatherings or high-risk settings.
Monitoring for symptoms is especially critical for people who have not been vaccinated with the MMR vaccine. We will update locations as necessary.
What to do if you may have been exposed and aren’t feeling well
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 that usually starts several days later on the face and spreads.
If you were at one of these locations during the exposure window and develop symptoms, immediately contact your health care provider by phone. If you do not have a provider, call an urgent care center or emergency department and explain that you may have been exposed to measles. Calling ahead helps prevent additional exposures.
Protecting yourself and others
If you are unvaccinated or not fully vaccinated, it is especially important to closely monitor for symptoms during the 21 days after a possible exposure. For future cases, MMR vaccine, given within 72 hours after exposure, can prevent infection. Unvaccinated individuals or those unsure of their immunity should talk to their health care provider about receiving the MMR vaccine.
CDPHE strongly recommends that all Coloradans ensure they and their children are up to date on MMR vaccinations. The first dose of MMR vaccine is routinely given at age 12 months. Families with infants too young to be vaccinated against measles should reconsider travel to areas in the U.S. and abroad with ongoing measles outbreaks. If travel cannot be avoided, infants 6-11 months should receive an early dose of MMR before traveling to outbreak areas.
Adults should have received 1 or 2 doses (depending on risk factors), unless they have other presumptive evidence of immunity to measles, such as those born before 1957 who are generally considered immune. There are also a small number of adults who received the inactivated measles vaccine during childhood from 1963 through 1967 who are considered unvaccinated and should receive at least one dose of MMR vaccine.
More information about MMR vaccines for children and adults can be found on the Centers for Disease Control and Prevention’s website.
Coloradans can check their or their child’s immunization records through the Colorado Immunization Information System (CIIS) Public Portal. Please note that records may be incomplete if all vaccines have not been reported by providers. Please call ACPHD with any questions, concerns, or for more information about measles symptoms, vaccines, or necessary actions, 970-264-2409.