San Francisco confirmed its first measles case since 2019 in an unvaccinated infant exposed to the virus while traveling internationally. The infant, younger than 12 months old, became infectious after returning to San Francisco and is currently recovering at home. All household members are reportedly vaccinated. The case was confirmed on a Monday evening.
California is battling one of its worst measles outbreaks since 2019, with 39 confirmed cases as of Monday before the San Francisco case. No deaths have been reported. Last month alone, nine related cases were reported in Placer and Sacramento counties, where at least 19 cases have been confirmed amid an ongoing outbreak, including exposure at a pediatric care setting.
The rise in measles overlaps with national resurgence. In 2025, the U.S. reported its highest number of measles cases in 30 years, driven mostly by large outbreaks in Texas and South Carolina. The country declared measles eliminated in 2000, but that status is now at risk.
Vaccine Effectiveness and Travel Risk
The measles virus is highly contagious, spreading easily through the air when infected persons breathe, talk, or cough, lingering in the air for up to an hour. Symptoms include fever, cough, runny nose, and pink eye, followed 2-4 days later by a rash. Two doses of the MMR vaccine are 97% effective at stopping illness, with the standard schedule being the first dose at 12-15 months and the second at 4-6 years old.
Dr. Susan Philip, San Francisco’s health officer, highlighted the risk: “It is incredibly important to get the MMR vaccine, as measles is one of the most infectious diseases in the world. If you and your family are traveling internationally, make sure everyone is up to date with the MMR vaccine and is aware of the symptoms of measles.”
Babies younger than 12 months cannot receive routine MMR vaccination and are especially vulnerable to infection. Health officials advise parents to consult health care providers before international travel. Parents can secure an early MMR vaccination for children as young as 6 months old due to measles risk abroad if unvaccinated.
This article is an AI-assisted summary. All facts and figures are drawn from the original report: https://ww2.kqed.org/news/2026/04/15/measles-san-francisco-baby-mmr-vaccines-international-travel-children-outbreak/