San Mateo County health officials have confirmed a positive measles case in an unvaccinated adult who recently traveled outside the United States, marking an unwelcome development as public agencies keep close watch on the disease. Investigators say they are working to reach anyone who may have been exposed, and so far no additional symptomatic cases have been reported. If verified as California’s first measles case of 2026, it lands amid a national uptick in measles that public health agencies have been tracking since last year. Officials are urging residents to review their immunization records and to contact a provider if they develop symptoms that could be measles.
San Mateo Health Details
San Mateo County Health confirmed the case to KQED, noting that the patient was unvaccinated and had recently traveled internationally. County communications officer Preston Merchant told the station that investigators are reaching out to possible exposures and that "so far no one else has developed symptoms." Officials also pointed out the county previously managed a travel-associated measles case in 2025, so this playbook is unfortunately familiar.
National Context
The Centers for Disease Control and Prevention has reported three confirmed measles cases in the United States so far in 2026, with cases in North Carolina and South Carolina, according to CDC data. The agency recorded 2,144 confirmed measles cases nationwide in 2025, the highest total in decades. Public health experts say many of the recent outbreaks have been driven by imported cases and by clusters of people who are not adequately vaccinated.
Bay Area Exposure Concerns
The San Mateo case follows a December 29, 2025, announcement from Contra Costa Health that a separate measles infection had been confirmed and that the infected person was contagious in public between December 17 and December 24, with possible exposures at several retail locations and a hospital emergency department, Contra Costa Health said. Contra Costa officials reported they are conducting contact tracing and notifying local providers to stay alert for new cases. That earlier incident served as a reminder of how quickly measles can spread in crowded public places, officials warned.
Symptoms, Risk and Vaccination
According to the CDC, measles symptoms usually start with fever, cough, runny nose and red eyes, followed a few days later by a spreading rash. Symptoms can appear seven to 21 days after exposure. About one in five unvaccinated people who get measles will require hospitalization, and the agency notes that complications can be especially serious for infants, pregnant people and those who are immunocompromised. California’s overall kindergarten MMR vaccination coverage remains high, but gaps in coverage at the local level can leave pockets of residents vulnerable to outbreaks.
What To Do If You Were Exposed
If you think you were exposed to measles, health officials advise calling your health care provider before showing up for care so clinics can take precautions and confirm your vaccination status. San Mateo County Health maintains local resources on vaccination and travel guidance and recommends MMR vaccination for people without evidence of immunity, according to San Mateo County Health. Local clinics, pharmacies and county-run sites can provide the vaccine to eligible people.
