California public health officials confirmed the state’s first case of a more severe mpox strain in San Francisco, marking the seventh detection of clade I since November 2024 and triggering renewed vaccination urgings ahead of summer travel and large gatherings.
The case, identified in an unvaccinated individual who had close contact with someone recently returned from abroad, was reported by the San Francisco Department of Public Health on Tuesday and confirmed by state authorities on Friday. The patient was hospitalized but is recovering, according to multiple municipal and state health bulletins.
This represents the first documented clade I infection in San Francisco, distinct from the clade II strain that drove a local outbreak in 2022. Statewide, California has recorded 14 weekly cases of the less severe clade II variant in 2026, nearly all in unvaccinated individuals.
Health officials emphasized that clade I is historically associated with more severe outcomes, though current data does not confirm whether it causes worse illness than clade II in the U.S. Context. The U.S. Centers for Disease Control and Prevention has separately warned clinicians about the spread of a dangerous mpox strain in Africa, though no direct link to the California case was established in state communications.
Transmission occurs primarily through prolonged skin-to-skin contact, including during sexual activity, with public health data indicating most reported cases involve gay, bisexual, and other men who have sex with men, as well as transgender individuals who have sex with men.
For more on this story, see San Francisco Reports First Case of Clade I Mpox.
Dr. Erica Pan, director of the California Department of Public Health and state public health officer, urged high-risk individuals to receive both doses of the mpox vaccine, noting the vaccine’s safety profile even for immunocompromised people, including those living with HIV or on immunosuppressive therapy.
Vaccination is not recommended for those who have previously had mpox. Doses are available through healthcare providers and local pharmacies, with uninsured or underinsured individuals directed to San Francisco’s resource portal at sf.gov/mpox for access assistance.
Symptoms typically initiate with fever, swollen lymph nodes, and fatigue, followed by a rash resembling pimples or blisters that often concentrates on the face, palms, and soles. Health departments across the Bay Area have intensified contact tracing and surveillance to detect additional cases and prevent further transmission.
How many doses of the mpox vaccine are recommended for full protection?
Two doses are recommended for full protection against mpox, particularly for individuals at high risk of exposure.
Is the mpox vaccine safe for people with weakened immune systems?
Yes, health officials confirm the vaccine is safe for immunocompromised individuals, including those living with HIV or taking immunosuppressive medications.
Where can uninsured residents in San Francisco acquire the mpox vaccine?
Uninsured individuals can find vaccination locations through the city’s public health website at sf.gov/mpox, which lists clinics and pharmacies offering low- or no-cost options.