California Officials Warn of Measles Exposure in 6 Counties Due to Infected Passenger

California health officials are issuing a warning about potential measles exposure across multiple counties, following a journey made by an infected Amtrak passenger who traveled nationwide via trains and buses.

The California Department of Public Health reported that the unvaccinated individual traversed the state using Amtrak trains and associated bus routes, affecting at least six counties: Alameda, Butte, Kern, Los Angeles, Sacramento, and San Joaquin.

Measles is known to be a highly contagious viral illness. According to health officials, unvaccinated individuals, especially young children and pregnant women, are at the greatest risk of experiencing severe illness or even death.

The individual arrived in California via an Amtrak train to Los Angeles on September 10. After reaching Los Angeles, the traveler continued on to Bakersfield, then Stockton, Oroville, Sacramento, and Emeryville, before leaving the state for Denver.

Here’s a breakdown of the passenger’s route:

• September 10: Departed Chicago at 1:30 p.m.
• September 12: Arrived at Los Angeles Union Station at 8:12 a.m.
• September 12: Left Los Angeles at 10:55 a.m., arriving at Bakersfield station at 1:45 p.m.
• September 12: Departed Bakersfield at 2:02 p.m., arriving at Stockton—San Joaquin St Station at 6:29 p.m.
• September 12: Left Stockton at 6:15 p.m., reaching Oroville bus/thruway stop at 6:05 p.m.
• September 13: Departed Oroville at 4 p.m., arriving at Sacramento Valley Station at 6:05 p.m.
• September 13: Departed Sacramento at 6:53 p.m., arriving at Emeryville Station at 8:36 p.m.
• September 14: Left Emeryville at 8:25 a.m., arriving in Denver at 6:59 p.m.

Officials advised that anyone who was on these trains or buses, or who visited the stations during these dates, may have been exposed to measles. They are currently coordinating with federal and local health departments to notify those potentially affected.

Dr. Rita Nguyen, the Assistant State Public Health Officer, emphasized the significance of vaccination against measles, stating, “This case, along with previous measles outbreaks in California this year, serves as a reminder of the importance of vaccination.” She recommended the measles-mumps-rubella (MMR) vaccine, which is safe and offers long-lasting protection against the disease, highlighting that vaccination is crucial not only for individual protection but also for safeguarding families and those too young to get vaccinated.

As of September 14, 2026, California had reported a total of 59 measles cases across 13 counties. Alarmingly, 94 percent of patients were either unvaccinated or had an unknown vaccination status.

What to Do If You Have Been Exposed or Have Symptoms

Health officials advise monitoring for symptoms, including fever and/or an unexplained rash, from seven to 21 days following exposure. If symptoms appear, it’s important to contact a healthcare provider for advice.

If there are concerns about measles, it is best to reach out to a healthcare professional before visiting any medical facility, to prevent exposing others.

Those who are unvaccinated against measles, or who are uncertain about their vaccination status, should consider contacting their healthcare provider about getting vaccinated. Officials recommend two doses of the vaccine to achieve full immunity.