GRAND JUNCTION, Colo. — Colorado has reported its fourth confirmed case of measles this year, marking the latest in a string of infections that health officials say could have been avoided through vaccination.

The Denver Department of Public Health confirmed that an adult in Denver County contracted the disease through household exposure to a baby who recently returned from Mexico. The infant, officials said, was too young to receive the measles-mumps-rubella (MMR) vaccine, highlighting a persistent vulnerability in population-level immunity.

Household Exposure Sparks Alarm

The infected adult was quarantined shortly after diagnosis, according to a CBS report cited by city officials. No public exposure sites have been identified in this case, but authorities continue to monitor the situation closely, tracing any potential indirect contacts.

“This case reminds us that measles is highly contagious and can spread rapidly, especially in settings where individuals are unvaccinated or cannot be vaccinated,” a Denver public health spokesperson said in a statement.

The case comes just weeks after Colorado recorded its first three measles infections of 2025, including one involving community exposure at Denver International Airport, sparking a multi-agency contact tracing effort.

The Source: Infant Returned from Mexico

According to public health authorities, the infant in question recently traveled to Mexico with family before returning to Colorado. Mexico has reported intermittent measles outbreaks in recent years, exacerbated by declines in routine vaccination during the COVID-19 pandemic.

Because the child was under 12 months old, they were not yet eligible for the MMR vaccine, which is typically administered between 12–15 months of age.

“This is a tragic illustration of how infants — even in well-vaccinated communities — are reliant on herd immunity for protection,” said Dr. Allison Keats, a pediatric infectious disease specialist at Children’s Hospital Colorado.

Measles: Still a Threat in the U.S.

Once declared eliminated in the United States in 2000, measles has resurged in recent years due to declining vaccination rates in some communities and increased international travel. The Centers for Disease Control and Prevention (CDC) has warned of the risk of domestic outbreaks tied to importation from countries with ongoing transmission.

Measles is caused by a highly contagious virus that spreads through airborne respiratory droplets. It can linger in a room for up to two hours after an infected person leaves.

Symptoms typically include:

• High fever

• Cough and runny nose

• Red, watery eyes

• Small white spots inside the mouth (Koplik spots)

• Rash that spreads from the face downward

Complications can include pneumonia, encephalitis, and even death, particularly in young children, pregnant individuals, and the immunocompromised.

Vaccination Still Key

Health officials across Colorado are renewing calls for widespread MMR vaccination, emphasizing that the vaccine is safe, effective, and widely available.

“Vaccination isn’t just a personal health decision — it’s a public health responsibility,” said Dr. Keats. “When you vaccinate, you protect people who can’t — like infants, cancer patients, and those with immune disorders.”

The MMR vaccine is 97% effective after two doses, according to the CDC. It is typically given in two stages: once at 12–15 months and again at 4–6 years of age.

Colorado has historically ranked below the national average in childhood vaccination rates, particularly in certain counties where philosophical or religious exemptions are common.

Officials Monitoring for Further Spread

The Colorado Department of Public Health and Environment (CDPHE) has not issued any additional public exposure alerts tied to the latest case but is continuing surveillance in conjunction with local and federal partners.

Authorities are urging anyone experiencing symptoms — particularly if they have recently traveled or come into contact with someone who has — to seek medical attention immediately and to call ahead before visiting a clinic, as measles can spread rapidly in health care settings.

While the current case count remains low, officials warn that even a single case can seed a wider outbreak, especially in undervaccinated populations.