An unidentified, unvaccinated traveler infected with measles traveled across multiple states via Amtrak trains and buses between September 10 and September 15, 2026. The California Department of Public Health (CDPH) issued an alert on Friday, September 18, after the individual was hospitalized following the five-day trip. The traveler’s route included a trip from Chicago to Los Angeles, followed by travel through six California counties and a final train ride to Denver.
State health officials are working with federal and local agencies to identify and notify individuals who may have been exposed at stations or onboard vehicles. The CDPH noted that scheduled arrival and departure times for the traveler's itinerary may differ from the actual times of travel. Dr. Rita Nguyen, California’s assistant health officer, stated that the case serves as a reminder of the importance of vaccination, noting that the infection can lead to permanent brain damage or death, particularly in children.
The United States is experiencing its highest measles caseload since 1991, with 3,471 confirmed cases reported by the Centers for Disease Control and Prevention (CDC) as of Friday, September 18. Outbreaks have been reported in 45 states and the District of Columbia this year. CDC data indicates that 95% of confirmed cases involve individuals who were either unvaccinated or had an unknown vaccination status. While Pennsylvania has reported four measles-related deaths, the CDC stated that the National Center for Health Statistics does not currently have 2026 death records listing measles as the underlying cause.
This exposure event affects passengers and staff who utilized Amtrak and local transit services across California and between major hubs like Chicago, Los Angeles, and Denver during the five-day window in mid-September. The scale of the national outbreak involves 3,471 people across 45 states and the District of Columbia, representing an infection rate of 13.2 cases per 1 million people. A person exposed to the virus would need to monitor for symptoms and verify their vaccination records, as health officials emphasize that vaccines are the primary defense against outcomes like brain damage. The CDPH has posted the traveler's itinerary online to assist the public in determining their own risk level based on their travel history.
Health and Human Services Secretary Robert F. Kennedy Jr. has attributed the U.S. cases to a global epidemic, while data from the World Health Organization places the U.S. 65th out of 169 countries for infection rates. This represents the worst 38 percent of reporting nations. What happens next depends on the success of contact tracing efforts and the potential for new cases to emerge from this specific travel route. Health officials have not provided a specific deadline for the end of the monitoring period, but the investigation into this traveler's contacts remains ongoing.