Santa Clara County health officials confirmed Saturday that a South Bay adult was infectious with measles while moving through San Francisco International Airport and two San Jose businesses on June 8 — potentially exposing hundreds of travelers and shoppers during peak World Cup travel season.

The County of Santa Clara Public Health Department is urging anyone who visited the listed locations during specified windows to check their vaccination records and monitor for symptoms for up to 21 days. The incident marks another measles alarm in the Bay Area just two months after an unvaccinated infant sparked a health alert in San Francisco — and comes as SFO is handling some of its highest international passenger volumes in years due to World Cup matches hosted across the region.

Health officials in Santa Clara County confirmed Saturday that an adult county resident traveled through San Francisco International Airport and visited two San Jose businesses while contagious with measles last Monday, June 8.

The resident — whose identity has not been disclosed — is believed to have contracted measles during international travel, according to the Santa Clara County Public Health Department (SCCPHD). Officials say the person was at SFO between 8:30 a.m. and 11 a.m. on June 8. That evening, between 8 p.m. and 10 p.m., the individual visited both the Trader Joe's on Coleman Avenue and the International Halal Market on East Santa Clara Street in San Jose.

Anyone who was at those locations during those time windows is considered at risk of potential exposure.

Why this matters now

Measles is one of the most contagious diseases on record. The virus can linger in an enclosed space — like an airport terminal or a grocery store — for up to two hours after an infected person has left, according to the CDC. With the FIFA World Cup drawing a surge of international travelers through SFO this summer, the timing sharpens the public health stakes: the airport has been among the busiest entry points into the country in recent weeks.

"Exposures like this one remind us of the importance of vaccination. Fortunately, the Bay Area region has strong community immunity, because of our very high rates of vaccination or from childhood exposure decades ago," said Dr. Sarah Rudman, Health Officer and Public Health Director for Santa Clara County, in a statement issued Saturday.

Dr. Rudman added: "Two shots of MMR or MMRV vaccine continue to be the best protection against measles and can stop a measles outbreak in its tracks, which is especially important during times of gathering and travel."

What to do if you were there

SCCPHD recommends the following steps for anyone who visited the affected locations at the listed times:

  • Check your vaccination records at MyVaccineRecord.cdph.ca.gov or through your healthcare provider.
  • If you are pregnant, an infant, immunocompromised, or unvaccinated, call your healthcare provider immediately.
  • Monitor for symptoms for 7 to 21 days after the potential exposure date (June 8). Symptoms include fever, cough, runny nose, red eyes, and a distinctive red rash that typically starts on the face.
  • If you develop symptoms, call ahead before visiting any clinic or hospital — this lets facilities protect other patients from exposure.
  • Avoid large gatherings if you believe you may have been exposed and are feeling unwell.

Context: A second measles alarm in two months

This is not the Bay Area's first measles alert of 2026. In April, San Francisco public health officials reported the city's first measles case since 2019, involving an unvaccinated infant who had traveled internationally. That alert prompted a broader regional conversation about vaccination rates among young children and international travelers.

The current case differs: the patient is an adult, the exposure spanned Santa Clara County and SFO, and the community at risk includes the working-age population that passes through two commercial corridors in San Jose.

Officials noted that the Bay Area's high overall vaccination rates mean widespread outbreak is unlikely, but urged residents who are unsure of their immunity status — including those vaccinated decades ago who may want to confirm two doses — to consult their physician.

Those seeking vaccination can contact their primary care provider or visit a county immunization clinic.