Napa and San Mateo counties confirmed two new measles cases on Wednesday — Napa County’s first measles patient since 2012. The announcements of the Bay Area’s second and third cases this year appear to make the region the home of California’s only reported measles cases in 2026 so far, amid outbreaks across the country of the highly contagious viral illness.
San Mateo County confirmed its second 2026 case of measles in a county resident Wednesday, after previously detecting an earlier case — the first measles detection in the state this year— on Jan. 8. Both patients are adults who had recently traveled outside the United States, according to county spokesperson Preston Merchant. San Mateo’s only 2025 case was also related to international travel, Merchant added.
The Napa County Health & Human Services Agency confirmed that its case of measles was in an unvaccinated child who became ill after traveling out of state to South Carolina, where the disease is currently surging. Health officials in the county have said there is no health risk to the general population, regardless of where in the Bay Area you are, and are working with the California Department of Public Health to notify anyone who may potentially have been exposed by the child.
Nonetheless, Dr. Christine Wu, public health officer for Napa County, urged anyone in the Bay Area who isn’t vaccinated to contact their healthcare provider and seek out the shot. “We don’t know when a case will pop up,” she said. “And so, your best protection is to get vaccinated at this point.”
While San Mateo’s first 2026 measles patient was unvaccinated, the second reported having received only one dose of the combined Measles, Mumps, and Rubella (MMR) vaccine as a child, which Merchant said San Mateo health officials haven’t yet been able to confirm.
Two doses of the MMR vaccine are recommended for maximum protection against measles.
But what if you were vaccinated against measles as a child, are you still up to date? Do you need a booster dose? Keep reading for what to know about measles in the Bay Area and around the country right now, how the measles vaccine works and which groups should speak to their health care provider about finding another shot.