California health officials issue measles exposure alert after Amtrak passenger travels through six counties

State health officials announced a measles exposure alert covering six California counties after an unvaccinated passenger traveled on Amtrak trains and connecting buses. The California Department of Public Health said the traveler moved through Alameda, Butte, Kern, Los Angeles, Sacramento and San Joaquin counties between September 10 and September 14, visiting stations in Los Angeles, Bakersfield, Stockton, Oroville, Sacramento and Emeryville before departing the state for Denver.

The department warned that anyone who rode the identified trains or buses, or who was present at the stations on those dates, could have been exposed to the highly contagious virus. Officials are coordinating with federal partners and local health agencies to notify potentially affected individuals.

"This case, along with previous measles outbreaks in California this year, serve as reminders of the importance of vaccination against measles," Assistant State Public Health Officer Dr. Rita Nguyen said in a statement. "The measles-mumps-rubella (MMR) vaccine is safe and provides long-lasting protection against measles. Vaccination protects both our own families and those who are too young to be fully vaccinated."

The department noted that, as of September 14, 2026, California has recorded 59 measles cases in 13 counties, with 94 percent of patients either unvaccinated or of unknown vaccination status. People who believe they may have been exposed are advised to watch for fever or rash within 7 to 21 days and to contact a health care provider before seeking in-person care. Unvaccinated individuals are encouraged to discuss receiving the two-dose MMR series with their doctor.