Mpox Cases Are Rising in San Francisco Again. From Symptoms to Vaccines, What to Know for Summer 2025
August 15, 2025
Mpox is rising again in San Francisco, where cases have spiked from one per month to 14 since late June. All involve clade II, the strain behind the city’s 2022 outbreak. Most recent infections are mild and in people who were already fully vaccinated, underscoring that vaccines do not eliminate risk but greatly reduce severity. Health officials emphasize that gay and bisexual men, as well as trans and nonbinary individuals, remain the most affected. With summer gatherings and travel underway, targeted vaccination, community awareness, and continued surveillance are critical to prevent a larger resurgence of mpox in the Bay Area.
Mpox has returned to San Francisco with a small but significant rise in cases. Since late June, 14 residents have been diagnosed, compared with just one case per month earlier in 2025. All infections are from clade II, the less severe strain that drove the Bay Area’s 2022 outbreak. While cases so far have been mild and no hospitalizations reported, officials stress the importance of vigilance. Notably, most infections occurred in people who had received both doses of the Jynneos vaccine, confirming that breakthrough cases occur. Yet as with COVID-19, vaccination remains essential for reducing severity, hospitalization, and death.
Patterns echo earlier outbreaks. Gay and bisexual men, along with transgender and nonbinary individuals who have sex with men, remain disproportionately affected. Seasonal factors may be driving the surge, as past increases have coincided with major events such as Pride and fall festivals. The San Francisco Department of Public Health has urged vaccination for high-risk groups, including those living with HIV, individuals on PrEP, and sex workers. Vaccination is also recommended for travelers to countries with active clade I and clade II outbreaks, given the potential for international spread.
The return of mpox raises urgent questions about sustained protection and public health readiness. While the current increase is small compared to 2022, officials caution against complacency. Clade I outbreaks in Africa remain a global emergency, and imported cases have already been detected in the United States. In this context, surveillance, rapid testing, and community engagement are as important as vaccination.
San Francisco’s experience highlights the evolving challenge of managing mpox: vaccines mitigate but do not eliminate risk, and outbreaks can reemerge when vigilance wanes. A strong, sustained public health response will be required to prevent a larger resurgence.