California health officials have issued a warning regarding possible exposure to measles in six counties following travel by an unvaccinated passenger on Amtrak trains and buses. The person with measles visited multiple locations, including the Bay Area and Alameda County. The California Department of Public Health (CDPH) is notifying the public about these potential exposures, urging unvaccinated individuals to take precautions. The warnings extend to various transport hubs, including Union Station. Residents are encouraged to be vigilant and aware of the situation as officials work to prevent further spread of the disease.