The fourth confirmed measles case was reported in Los Angeles County this year, according to the Los Angeles County Department of Public Health. All four measles cases occurred due to international travels.
As of Thursday, Feb. 20, the CDC has confirmed nearly 1,000 cases of measles in the U.S. in 2026, which is about four times the number of cases reported in all of last year.
In a campus health briefing with Annenberg Media, USC Chief Campus Health Officer Dr. Sarah Van Orman said the leading cause of the measles outbreak is declining vaccination rates across the country.
In the year 2000, the U.S. was declared “measles free,” with no reported spread of the disease in the country. Vaccination rates floated around 95%, providing “herd immunity,” meaning enough people were immune so that the disease was unlikely to spread, she continued. Vaccination rates for measles have since dropped between 70% and 80%.
Van Orman said the anti-vaccination movement was likely inspired by Andrew Wakefield’s study on an alleged causation between measles, mumps and rubella (MMR) vaccinations and autism spectrum disorder.
However, scientific evidence has proven that there is no direct link between the two.
The university began emergency preparations about five years ago in lieu of a potential disease outbreak.
Measles is a viral airborne illness that causes inflammation of the lining of the brain, and can lead to permanent brain damage if left untreated. Since the loss of herd immunity, a single case is a public health emergency and risks rapid spread, Van Orman said.
A person contagious with measles is not immediately symptomatic. Symptoms can be present four days before the commonly identifying rash appears.
“People who have measles are walking around spreading the measles way before they realize that they’re ill,” Van Orman said.
Van Orman added that every room a contagious measles patient walks in is considered exposed for four days, and any person who’d enter that room two hours after they left it would be as well.
While no antiviral treatment exists, measles is a vaccine-preventable disease, and she recommends the public to aim to regain herd immunity.
“The most important thing is to know your immune status,” said Van Orman.
She encouraged USC students and employees with an unknown measles status to receive a blood test at the Engemann Student Health Center. The test indicates if the body has a protective level of antibodies against the virus.
Anyone exempt from the university’s vaccine requirements is encouraged to speak with a healthcare professional at Keck about minimizing the risk of exposure.
Those who are potentially contagious of the measles can call the 24/7 nurse hotline 213-740-9355 (WELL) to discuss a care plan.