California health officials warned of a possible measles exposure after an unvaccinated, infected traveler rode Amtrak trains and connecting Thruway buses through six counties, arriving in Los Angeles on Sept. 10 and later leaving for Denver. Authorities are notifying passengers and station visitors who may have been exposed. The alert comes as the U.S. faces its largest measles resurgence in decades, with Pennsylvania reporting 731 cases and at least four deaths. Officials emphasize the importance of the safe and effective MMR vaccine to prevent further spread.
California Issues Measles Exposure Alert After Unvaccinated Passenger Traveled Through Six Counties on Amtrak
Pennsylvania has seen four measles-related deaths as the US grapples with the fallout from increasing vaccine hesitancy.Photograph: efired/Getty Images
California public health officials have issued a statewide alert after an unvaccinated, measles-infected traveler moved through at least six counties on Amtrak trains and connecting Thruway buses, potentially exposing fellow passengers and people at transit stations.
The California Department of Public Health (CDPH) said the individual entered the state on an Amtrak service that arrived in Los Angeles on Sept. 10. The traveler then continued to Bakersfield before traveling through Stockton, Oroville, Sacramento and Emeryville and ultimately left California for Denver. The counties involved include Los Angeles, Kern, San Joaquin, Butte, Sacramento and Alameda.
Who May Have Been Exposed
Health officials warned that anyone who rode the same trains or Thruway buses on the listed dates, or who was inside the stations along the route during that time, may have been exposed to measles. The state is coordinating with federal partners and local public health departments to identify and notify potentially exposed individuals.
"This case, along with previous measles outbreaks in California this year, serve as reminders of the importance of vaccination against measles," said 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."
Context: A Growing U.S. Resurgence
The alert comes amid the largest U.S. measles resurgence in more than three decades, a wave public health experts largely attribute to rising vaccine hesitancy. Pennsylvania is currently reporting the nation's worst active outbreak, with state officials confirming 731 cases across 38 counties this year and stating that at least four people have died from measles-related illness.
Pennsylvania has requested emergency assistance from the U.S. Centers for Disease Control and Prevention (CDC) as the outbreak spreads. State officials warned the request could be withdrawn unless the CDC publicly recognizes the four measles-associated deaths — a step they say U.S. Health Secretary Robert F. Kennedy Jr. previously advised the agency not to take.
Controversy and Other Exposure Incidents
Robert F. Kennedy Jr. recently headlined a conference for the anti-vaccine group Children’s Health Defense. Public health experts have criticized the event for promoting unproven claims about vaccine safety at a moment when officials are urging community vaccination to curb transmission.
Earlier this week, officials in Missouri also reported a mass-exposure incident after a person with measles traveled by Amtrak from Sedalia to Chicago, exposing more than 250 people in Jackson County alone.
Separately, the CDC has shifted to using data from the National Center for Health Statistics to count measles deaths during the outbreak — a change typically made to track longer-term mortality trends. Federal officials have not provided a clear explanation for the timing of this adjustment.
What You Can Do
Public health authorities urge anyone who may have been exposed to monitor for symptoms (fever, cough, runny nose, red eyes and the characteristic rash) and to contact their local health department or healthcare provider. Those who are unsure of their vaccination status are advised to seek MMR vaccination — which is safe, effective and provides durable protection against measles.
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