Colorado officials declare measles outbreak in Adams County after third person connected to school contracts illness

Colorado health officials declared a measles outbreak in Adams County on Wednesday after a third person connected to Broomfield High School contracted the illness.

The new case marks the third case among three unvaccinated people, two of whom are confirmed to be students at the school, according to the Colorado Department of Public Health and Environment. The U.S. Centers for Disease Control and Prevention defines an outbreak as a cluster of three or more related cases.

"The child is a known contact of a recent measles case tied to Broomfield High School," a department spokesperson said. "Students and staff who may need to take additional health precautions will be contacted directly by local public health officials and school administrators. Other exposures for this individual are under investigation."

In addition to the locations provided by health officials regarding the previous two cases, they say that if you were in the following locations at the following times, you should monitor your health for symptoms:

• Broomfield Heights Middle School, 1555 Daphne Street, from 8:30 a.m. to 6 p.m. on Feb 17, 18, and 19
• Broomfield Community Center, 280 Spader Way, from 7:35 to 10:30 p.m. on Feb. 19

Measles symptoms can develop within 21 days of exposure and start with fever, cough, runny nose, and red eyes. Then, a rash often develops several days later on the face and spreads to other parts of the body. Health officials are urging people who think they may have been exposed to contact their health provider or a doctor.

If you aren't vaccinated for measles, mumps, and rubella and may have been exposed, you can still get it within 72 hours of exposure to prevent illness. Immunoglobulin given within six days can also help prevent or lessen illness, officials say.

The first case stemming from the school was confirmed last week and the second case was confirmed on Monday. The names, ages, and genders of the students were not released by health officials.

The Boulder Valley School District says out of 1,669 students at Broomfield High School, 26 are on their exclusion list and not allowed to attend class.

Broomfield is about 15 miles northwest of Denver.

According to the CDC, there have been 10 new measles outbreaks in 2026, and 90% of confirmed cases — 1,023 of 1,136 — are "outbreak-associated." Of the outbreaks the CDC is tracking, 152 cases are new from 2026, and 871 are from outbreaks that started in 2025.

Almost all cases, the CDC says, are also among those who aren't vaccinated for measles or whose vaccination status isn't known:

• Unvaccinated or Unknown: 97%
• One MMR dose: 1%
• Two MMR doses: 2%

The number of measles cases in the U.S. has fallen dramatically since the advent of the vaccine in 1963. Prior to that, the country typically saw hundreds of thousands of cases each year.

Health experts point to lower vaccination rates as a reason for increases in preventable diseases like measles.

Last year, the U.S. recorded the highest number of measles cases in more than 30 years, federal data shows.