Second Measles Case Confirmed in Denver, Health Officials Warn

DENVER, Colo. — Health officials confirmed Monday that Colorado has its second case of measles this year, involving an unvaccinated infant under the age of 1 in Denver County. The infant recently traveled with family to Chihuahua, Mexico, which is experiencing an ongoing measles outbreak.

The case was announced in a joint statement from the Colorado Department of Public Health and Environment (CDPHE) and the Denver Department of Public Health and Environment. Dr. Rachel Herlihy, state epidemiologist and deputy chief medical officer at CDPHE, emphasized the vulnerability of infants, stating, “Infants under 12 months are especially vulnerable to measles because they are typically too young to be vaccinated.”

CDPHE officials are urging residents to verify their vaccination status and to be vigilant for symptoms of measles, which include fever, cough, runny nose, red eyes, and a rash that typically begins on the face and spreads. People who visited the Denver Health emergency department between 10:30 a.m. and 4:30 p.m. on April 6 may have been exposed to the virus, according to the announcement.

Health officials added that the risk of exposure is increased due to Colorado’s below-threshold vaccination rate, which is necessary to achieve herd immunity against measles. “The community immunity or herd immunity threshold for measles is about 95 percent. So statewide we are falling short of that,” said Herlihy in a press conference.

Prior to this case, Colorado reported one additional case in March involving an unvaccinated adult from Pueblo who also traveled to Mexico, where there is a confirmed outbreak. According to the federal Centers for Disease Control and Prevention, measles cases nationally are on the rise, with two deaths reported this year and hospitalization rates hitting 12 percent.

Herlihy urged families planning travel to areas known for outbreaks to consult healthcare providers about early vaccination options for infants, stating, “This case is a stark reminder that families traveling internationally should delay unnecessary travel or talk to their health care providers about early MMR vaccination for infants.”

The MMR vaccine, which protects against measles, mumps, and rubella, is generally administered to children at 12 to 15 months of age, with a second dose by age 4. Two doses are about 97 percent effective at preventing measles.

As of early April 2025, the U.S. has reported an increase in measles cases compared to previous years. In addition to Colorado, several other states including Alaska, California, Georgia, and New York have confirmed cases.