California Measles Warning: Six Counties Exposed on Amtrak Route 2026

California measles warning: state health officials have issued an alert after an unvaccinated, infected passenger traveled through six counties on Amtrak trains and thruway buses, potentially exposing thousands to the highly contagious virus.

The traveler entered California on an Amtrak train that arrived in Los Angeles on September 10, then continued to Bakersfield, Stockton, Oroville, Sacramento, and Emeryville before leaving for Denver. The counties involved are Alameda, Butte, Kern, Los Angeles, Sacramento, and San Joaquin. This incident comes amid the largest measles resurgence in the U.S. in over three decades, driven largely by vaccine hesitancy.

Measles Exposure: What You Need to Know

Measles is one of the most contagious viruses known. It can linger in the air for up to two hours after an infected person leaves a room. Symptoms typically appear 7–14 days after exposure and include high fever, cough, runny nose, red eyes, and a characteristic rash.

Health officials are working with federal and local partners to identify and notify anyone who may have been exposed—whether on the same trains or buses, or inside the stations along the route on the affected dates. If you were in these locations, monitor for symptoms and contact your healthcare provider immediately if you feel unwell.

Who Is Most at Risk?

Certain groups face higher risks of severe complications, including pneumonia, encephalitis, and even death. The elderly and immunocompromised are particularly vulnerable, as are unvaccinated infants and pregnant women.

• Elderly adults may have waning immunity or underlying health conditions.
• Unvaccinated individuals have a 90% chance of infection if exposed.
• Immunocompromised people cannot always receive live vaccines.
• Pregnant women risk miscarriage, premature birth, or low birth weight.

Vaccination: Your Best Defense

The MMR (measles-mumps-rubella) vaccine is safe and highly effective. Two doses provide about 97% protection against measles. Health officials urge everyone to check their vaccination status, especially before travel.

“This case, along with previous measles outbreaks in California this year, serve as reminders of the importance of vaccination against measles,” said assistant state public health officer Rita Nguyen.

What to Do If You Were Exposed

If you were on any of the affected Amtrak trains or buses, or in the stations along the route on the dates involved, you may have been exposed. Contact your healthcare provider, especially if you are unvaccinated or unsure of your status. Do not visit a clinic without calling ahead to avoid exposing others.

FAQ

Stay informed, check your vaccination records, and help prevent the spread of measles in your community.