A measles-infected traveler crisscrossed California by Amtrak trains and buses before being hospitalized, prompting state health officials to warn thousands of passengers who may have been exposed.
The unvaccinated traveler passed through six California counties over three days — Los Angeles, Kern, Sacramento, San Joaquin, Alameda and Butte — before continuing on to Denver, according to the California Department of Public Health.
The traveler arrived in Los Angeles from Chicago aboard an Amtrak train on Sept. 12.
Over the next three days, the infected passenger traveled by train and thruway buses, stopping in Los Angeles, Bakersfield, Stockton, Oroville, Sacramento and Emeryville before heading to Denver.
The exact routes and stations, along with the times when exposure may have occurred, can be found here.
Anyone who was present at those locations during the specified time frames may have been exposed, officials said.
Authorities warned that symptoms could appear seven to 10 days after exposure and include fever, cough, runny nose, red eyes and rash.
“Measles is one of the most contagious infections that can lead to severe life-long consequences including permanent brain damage and can also be fatal, especially for children,” said Dr. Rita Nguyen, Assistant State Public Health Officer.
“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.”
Unvaccinated individuals are being urged to quarantine, avoid large gatherings and monitor for signs of illness for up to three weeks.
Officials also stressed that pregnant women, infants, immunocompromised individuals and the unvaccinated should seek medical guidance immediately if exposure is suspected.
State health officials are coordinating with the federal partners and local health officials on contact tracing tied to the exposure sites.
“With this news, and with measles spreading in other parts of the United States and the world, CDPH urges Californians to ensure they are fully vaccinated against measles,” a press release from the CDPH read.
Anyone who develops symptoms should contact a medical provider before showing up in person, health officials warned, to reduce the risk of spreading the highly contagious virus.
California has recorded 59 measles cases as of Sept. 14, 2026, according to state health officials.
State data shows 94% of those cases involved people who were unvaccinated or whose vaccination status was unknown.
