Rare Mpox Strain Detected In San Francisco
- Health officials report mpox cases rising in California and a rare strain was detected for the first time in San Francisco. - Officials urge vaccination and caution amid increasing case counts to limit spread within vulnerable communities. - Public-health responses include surge vaccination efforts and surveillance to track the rare strain's spread ( patch.com ).
San Francisco has confirmed its first clade I mpox case, as California health officials warn that mpox infections are rising statewide. (sf.gov) The San Francisco Department of Public Health said April 14 that the case involved an unvaccinated adult who was hospitalized and is improving. The person reported close contact with someone who had traveled internationally. (sf.gov) Mpox is a viral disease that can cause rash, fever and painful lesions, and health officials divide it into two main groups: clade I and clade II. The 2022 U.S. outbreak was driven by clade II, while clade I has drawn closer monitoring because it has been linked to more severe illness in some outbreaks. (cdc.gov) (sf.gov) California’s health department said April 17 that vaccination protects against both clade I and clade II and urged people at higher risk to get both doses. The agency said risk to the general public remains low. (cdph.ca.gov) State officials said mpox activity has been climbing in 2026 after lower levels in 2024 and 2025. A California public-health summary cited by local agencies said the state was averaging 14.5 weekly cases in 2026, up from 5.8 in 2024 and 3.4 in 2025. (changeflow.com) (cdph.ca.gov) San Francisco has seen the same pattern locally. The city said 24 residents were diagnosed with clade II mpox from January through March 2026, compared with fewer than 10 cases in the first quarter of prior years. (sf.gov) Federal data show the San Francisco case is part of a small but growing national count of clade I infections. City officials said 15 clade I cases had been reported in the United States over the previous two years, including six in California, before the San Francisco case was announced; KQED reported the San Francisco case brought the U.S. total to 16. (sf.gov) (kqed.org) Health officials are focusing on vaccination, case finding and surveillance rather than broad public restrictions. San Francisco said people without insurance or with trouble accessing care can use city vaccine locations listed through its mpox information page. (sf.gov) Officials have also tied this case to travel-linked exposure, not wider community spread in the city. For now, the state and city message is to push vaccination before summer travel and events that have coincided with past increases. (sf.gov) (cdph.ca.gov)
