California public health officials have issued a warning after an unvaccinated individual diagnosed with measles traveled across the state on Amtrak trains and buses, raising concerns about potential exposure to the highly contagious virus. The passenger, who was later hospitalized, journeyed through multiple counties including Alameda, Butte, Kern, Los Angeles, Sacramento, and San Joaquin in early to mid-September.

According to the California Department of Public Health, the individual traveled from Chicago to Los Angeles by train between September 10 and 12, spending several hours at Los Angeles Union Station before continuing to Bakersfield, Stockton, Oroville, Sacramento, and Emeryville. The passenger subsequently arrived in Denver on Tuesday. Exact departure and arrival times are approximate, reflecting scheduled train and bus times.

Officials have urged anyone who was aboard the same trains or buses, or who was present at the affected stations on the relevant days, to be aware of potential measles exposure. The department is encouraging Californians to verify their vaccination status, emphasizing the importance of the measles-mumps-rubella (MMR) vaccine in preventing infection.

"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. She highlighted that the MMR vaccine is safe and provides durable immunity, protecting both individuals and vulnerable populations unable to be vaccinated.

Health officials advised that persons who are not fully immunized or unsure of their vaccination status should consult a healthcare provider about receiving the vaccine. Those exposed to the virus less than a week prior are advised to seek vaccination or immune globulin treatment for prevention. Individuals exposed between one and three weeks ago should self-isolate and monitor symptoms for 21 days.

To prevent further spread, anyone experiencing symptoms consistent with measles, such as fever or an unexplained rash, should contact medical providers before visiting healthcare facilities in person.

This year, California has reported 59 confirmed measles cases across 13 counties. More than 90% of these infections occurred in individuals who were either unvaccinated or whose vaccination status could not be confirmed. Public health officials continue to stress vaccination as the most effective measure to control outbreaks and protect public health.