CDC

Colorado measles outbreak traced to air traveler

February 2, 2026

A May–June 2025 measles outbreak in Colorado was associated with an infectious traveler who passed through Denver International Airport, resulting in nine secondary and one tertiary case among state residents, plus seven cases in other jurisdictions. Four secondary cases occurred in fully vaccinated adults, who experienced fewer and milder symptoms. Notably, two vaccinated patients had negative nasopharyngeal PCR results but positive urine PCR findings, highlighting diagnostic challenges. Three unvaccinated people and one with unknown vaccination status were hospitalized; all recovered. Rising case counts parallel broader increases in U.S. measles activity since early 2025.

Clinical takeaway: Ensure patients, especially travelers, are current on 2-dose MMR, and consider urine PCR testing when evaluating suspected measles in vaccinated individuals.

Source:

Metz AR, et al. (2026, January 29). CDC. Measles Outbreak Associated with an Infectious Traveler — Colorado, May–June 2025. https://www.cdc.gov/mmwr/volumes/75/wr/mm7504a1.htm