A passenger who traveled from Colorado to California on multiple Amtrak trains last week has been hospitalized with measles, raising concerns that other travelers may have been exposed to the highly contagious and potentially deadly infection.
The unidentified traveler reached California aboard an Amtrak route from Denver to Los Angeles between September 10 and 12, according to the California Department of Public Health, which announced the case Friday.
After arriving in Los Angeles, the passenger boarded another Amtrak train bound for Bakersfield and got off at Bakersfield Station.
The traveler then continued to Stockton, arriving at Stockton-San Joaquin Street Station, before taking a bus to Oroville. The following day, the passenger traveled by bus from Oroville to Sacramento and arrived at Sacramento Valley Station.
The journey continued from Sacramento to Emeryville, where the passenger arrived at Emeryville Station.
Between September 14 and 15, the passenger traveled from Emeryville back to Denver.
The itinerary passed through Alameda, Butte, Kern, Los Angeles, Sacramento and San Joaquin counties, according to health officials.
The travel timeline indicates that the passenger spent Saturday night in the Oroville area and stayed in the Emeryville area on Sunday night.
An unidentified passenger who traveled from Colorado to California on multiple Amtrak trains last week has been hospitalized with measles.
The passenger traveled by train and bus through Alameda, Butte, Kern, Los Angeles, Sacramento and San Joaquin counties in California. An Amtrak train is pictured.
California health authorities are coordinating with county health departments and federal agencies to locate and alert people who may have come into contact with the passenger.
“This case, along with previous measles outbreaks in California this year, serves as a reminder of the importance of measles vaccination,” Dr. Rita Nguyen, the state’s assistant public health officer, said in a statement.
“Measles is among the most contagious infections and can cause serious, lifelong complications, including permanent brain damage. It can also be fatal, particularly for children,” Nguyen said.
Officials are urging anyone who may have been exposed to review their immunization records. Two doses of the measles, mumps and rubella (MMR) vaccine provide full protection against the virus.
People who are unvaccinated or uncertain about their immunity should contact a health care provider to discuss receiving the vaccine, the California Department of Public Health advised.
Those who may have encountered the passenger should watch for symptoms for seven to 21 days and reduce contact with other people during that period.
Anyone who believes they may have measles should call a health care provider before visiting a clinic or hospital, helping prevent further exposure to patients and staff.
California has recorded 59 measles cases in 13 counties so far in 2026. In 94 percent of those cases, patients were either unvaccinated or had an unknown vaccination status.
MMR vaccines, shown inside a medical refrigerator, are generally administered in two doses: the first at 12 to 15 months of age and the second between ages four and six.
The case follows the death of an unvaccinated 18-year-old in Pennsylvania, who died “due to complications of measles,” according to reports.
Mifflin County Coroner Andrea Alcalde ruled that the teen died from acute disseminated encephalomyelitis, a rare and severe neurological condition associated with measles that causes inflammation in the brain.
No other details about the teenager were released.
Days earlier, health officials in the state announced an unvaccinated 40-year-old woman died last weekend from ‘complications associated with measles.’
The virus has spread rapidly across the country this year, with data from the Centers for Disease Control and Prevention (CDC) showing that as of September 11, there were 3,294 cases nationwide so far this year – well surpassing last year’s total of 2,289. About 95 percent of infections this year have been in unvaccinated individuals.
The above CDC map updated September 11 shows measles cases by state for 2026
Measles, which is highly infectious, is characterized by cough, fever, a distinctive blotchy rash that starts on the face before spreading down the body and tiny white spots inside the mouth called Koplik spots.
The virus spreads through direct contact with infectious droplets or through the air. Patients with a measles infection are contagious from four days before the rash through four days after the rash appears. Enclosed areas like airports and planes are extremely risky locations for disease transmission.
It first invades the respiratory system, then spreads to the lymph nodes and throughout the body. As a result, the virus can affect the lungs, brain and central nervous system.
While measles sometimes causes milder symptoms, including diarrhea, sore throat and achiness, it leads to pneumonia in roughly six percent of otherwise healthy children, and more often in malnourished children.
Though the brain swelling that measles can trigger is rare, occurring in about one in 1,000 cases, it is deadly in roughly 15 to 20 percent of those who develop it, while about 20 percent are left with permanent neurological damage, such as brain damage, deafness or intellectual disability.
Measles can also severely damage a child’s immune system, making them susceptible to other potentially devastating bacterial and viral infections they were previously protected against.
Before MMR vaccines became available in the 1960s, measles caused epidemics with up to 2.6 million global deaths every year. By 2023, that number had fallen to roughly 107,000 deaths.
Nationwide, 92.4 percent of kindergarteners are fully vaccinated against measles, below the CDC’s 95 percent threshold for herd immunity
