Western Riverside County Confirms Localized Measles Outbreak

The Centers for Disease Control and Prevention is reporting more than 910 measles cases nationwide in 2026, as local health officials confirm a new outbreak in Western Riverside County.

According to Riverside University Health System, an adult and a child have tested positive for measles in western Riverside County. Both cases may be linked to the county’s first confirmed case of the year, bringing the total number of confirmed measles cases locally to three.

Public health officials define an outbreak as three or more cases in a geographic area that are potentially connected — a threshold now met in western Riverside County.

Health authorities say they were alerted after a patient presented with symptoms consistent with measles. Immediate precautions were taken at the hospital or doctor’s office to limit potential exposure to others.

Despite one of the newly confirmed patients reporting being vaccinated, health officials stress that measles remains highly infectious. The virus can linger in the air for up to two hours after an infected person leaves an area, increasing the risk of transmission.

“If you’re in a room with 10 unvaccinated people and someone with active measles enters, nine out of those 10 people are likely to become infected,” health officials warned.

While many recover, measles can lead to serious complications, including irreversible health problems that can last a lifetime.

Public health leaders are urging residents to review their vaccination status, particularly before traveling internationally or to areas experiencing outbreaks. They also advise anyone experiencing symptoms — whether suspected to be measles, flu, COVID-19, or RSV — to isolate until fever-free and symptoms improve to prevent further spread.

As measles cases continue to rise nationwide, officials emphasize that vaccination remains the most effective protection against the virus.

To learn more about countywide efforts to track and mitigate the spread of measles you can go to Riverside University Health System's website.