A passenger who crossed from Colorado into California on multiple Amtrak routes last week has been hospitalized with measles, raising concerns that the highly contagious and potentially fatal virus may have exposed other travelers.
California Department of Public Health officials said Friday that the unidentified traveler rode an Amtrak train from Denver to Los Angeles between September 10 and September 12.
After reaching Los Angeles, the passenger boarded another Amtrak service bound for Bakersfield, arriving 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.
From Sacramento, the passenger took another route to Emeryville, arriving at Emeryville Station.
Between September 14 and 15, the passenger traveled from Emeryville, California, back to Denver.
The itinerary indicates that the traveler passed through Alameda, Butte, Kern, Los Angeles, Sacramento and San Joaquin counties.
It also suggests the passenger stayed overnight in the Oroville area last Saturday and spent Sunday night in the Emeryville area.
An unidentified passenger who traveled from Colorado to California on a series of Amtrak trains last week has been hospitalized with measles.
The passenger used trains and buses while traveling through Alameda, Butte, Kern, Los Angeles, Sacramento and San Joaquin counties in California. An Amtrak train is pictured.
California health officials are now working with county health departments and federal officials to identify and notify anyone who may have been exposed.
‘This case, along with previous measles outbreaks in California this year serve as reminders of the importance of vaccination against measles,’ Dr Rita Nguyen, assistant state public health officer, said in a statement.
‘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,’ she noted.
Health officials now urge anyone who may have been exposed to check their vaccination status as two doses of the measles, mumps and rubella (MMR) vaccine provide full immunization against the virus.
Anyone who is not fully vaccinated or is unsure of their immunity should contact a health care provider about vaccination, the California Department of Public Health suggested.
Those who may have been exposed to the passenger should also monitor their symptoms for seven to 21 days and limit interactions with others.
Anyone who suspects they have measles, meanwhile, should contact a healthcare provider before going to a medical facility to avoid potentially exposing others.
California has already reported 59 measles cases across 13 counties thus far in 2026. The vast majority, 94 percent, of those patients were either unvaccinated or did not know their vaccination status.
MMR vaccines (center) sit inside a medical refrigerator. The shot is typically given once between ages 12 and 15 months and again between ages four and six
The news comes just days after an unvaccinated 18-year-old from Pennsylvania died ‘due to complications of measles.’
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