Rare Mpox Strain Detected In San Francisco
- Health officials reported a surge in mpox cases across California and confirmed a rare strain in San Francisco. - The detection marks the first known appearance of this rare mpox strain in the city, officials said. - Public health authorities urge vaccination and monitoring to contain spread amid rising cases statewide (patch.com).
San Francisco health officials confirmed the city’s first clade I mpox case on April 14 in an unvaccinated adult. (sf.gov) The patient was hospitalized and is improving, and the person reported close contact with someone who had traveled internationally to an area where clade I mpox is circulating, the San Francisco Department of Public Health said. (sf.gov) California said this was the seventh identified clade I case in the state since November 2024 and the first in San Francisco. State officials said local health departments are doing enhanced surveillance and contact tracing. (cdph.ca.gov) Mpox is a virus that spreads mainly through close physical contact, and clade I is a different branch from clade II, the version that has circulated in California and the United States since 2022. California said community spread of clade I was identified in Southern California in October 2025. (cdph.ca.gov) San Francisco’s alert said clade II cases had usually stayed below 10 in the first quarter of prior years, but 24 city residents were diagnosed from January through March 2026. Officials said cases could rise again in summer and fall, when travel and large events have previously been linked to increases. (sf.gov) The city and state both said the current risk to the general public remains low, but they urged people at higher risk to get both doses of the JYNNEOS vaccine. The vaccine protects against both clade I and clade II, according to San Francisco health officials. (sf.gov) (cdc.gov) Nationally, the Centers for Disease Control and Prevention said 11 clade I cases were reported in the United States from November 2024 through February 2026, with five more reported since March 2026. The agency said those five newer cases were not linked to each other. (cdc.gov) San Francisco’s case count dashboard says mpox totals are updated Monday through Friday and can change as reports are confirmed. Health officials said people with a new rash or possible exposure should seek testing and care while the city tracks whether this first clade I case leads to additional infections. (sf.gov 1) (sf.gov 2)
