California reported its first measles case of 2026 in San Mateo County: an unvaccinated adult likely infected during international travel. Public-health teams are performing contact tracing while larger outbreaks continue elsewhere in North America, including 310 cases in South Carolina and about 390 cases near the Utah–Arizona border. Experts warn recent federal policy changes could weaken public confidence in vaccines, even as health officials stress that two doses of measles vaccine provide roughly 97% protection. Officials urge vaccination and prompt reporting of suspected exposures.
California Confirms First Measles Case of 2026 in San Mateo County As Vaccine Policy Debate Intensifies
A 1-year-old is held by his mother as he receives an MMR vaccine.(Jan Sonnenmair / Getty Images)
Barely more than a week into 2026, the California Department of Public Health confirmed the state’s first measles case of the year. The infection was identified in San Mateo County and, according to county health officials, involved an unvaccinated adult who likely acquired the virus during recent international travel.
Local Response: San Mateo County health officials say they are conducting contact tracing and monitoring anyone who may have been exposed. Preston Merchant, a county health spokesperson, said that so far contacts have reported no symptoms and that contact tracing remains the primary tool to limit spread.
"Right now, our best strategy to avoid spread is contact tracing, so reaching out to everybody that came in contact with this person," Merchant said. "So far, they have no reported symptoms. We’re assuming that this is the first [California] measles case of the year."
Growing Outbreaks Across North America
Measles outbreaks are expanding across the United States. The South Carolina State Department of Public Health reported its outbreak has reached 310 cases; the outbreak began with an infection in July and has since been linked to cases in North Carolina and Washington state. At the Utah–Arizona border, officials reported a separate cluster of roughly 390 cases tied to schools and pediatric care centers, according to the Utah Department of Health and Human Services.
Canada — long considered measles-free — lost its measles-elimination status after a large, multi-jurisdictional outbreak that began in October 2024, the Public Health Agency of Canada said in November.
Why This Matters
Measles is among the most contagious viruses known. The California Department of Public Health notes that viral particles can linger in the air for up to two hours after an infected person leaves a space. Last year the U.S. recorded about 2,000 measles cases, the highest annual total since 1992, according to the Centers for Disease Control and Prevention (CDC).
To lose measles-elimination status, a country must show sustained, ongoing transmission of the same locally circulating strain. Many recent U.S. cases were initially linked to international travel, which has helped the United States retain elimination status so far. However, prolonged domestic chains of transmission could prompt regional public health bodies to reassess that designation.
Policy Changes and Public Confidence
Public-health experts have raised concerns about recent federal-level policy shifts and leadership decisions that could influence vaccine uptake. Administration officials, including Health Secretary Robert F. Kennedy Jr., have advocated for changes to vaccine policy, and a presidential memorandum issued in December adjusted the federal guidance used for recommended childhood vaccines, according to official announcements and reporting. In June, the administration replaced members of a CDC vaccine advisory committee; critics and some public-health experts say such moves risk undermining public trust in routine immunization programs.
"Viruses and bacteria that were under control are being set free on our most vulnerable," said Dr. James Alwine, a virologist and member of the nonprofit Defend Public Health.
Symptoms, Prevention And Advice
Typical measles symptoms include cough, runny nose, conjunctivitis (pink eye) and a characteristic rash. The disease spreads through breathing, coughing or talking, and it often leads to hospitalization; in some cases it can be fatal.
The California Department of Public Health says two doses of the measles-containing vaccine provide about 97% protection against infection. Public-health officials continue to recommend vaccination for eligible children and adults and urge anyone who may have been exposed to contact local health authorities for guidance.
Local Note: San Mateo County also reported an unvaccinated child’s death from influenza this week.
This report draws on statements from county and state health departments and data from the CDC. This story originally appeared in the Los Angeles Times.
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