Mpox Rare Strain Detected In SF
- Mpox cases are rising across California, and health officials warn of increased transmission risk in San Francisco. - A rare mpox strain was detected for the first time in San Francisco, alarming public-health experts monitoring outbreaks. - Officials are urging vaccination and vigilance to curb spread, noting the discovery could affect local vaccine strategies (patch.com).
San Francisco confirmed its first clade I mpox case on April 14, in an unvaccinated adult who was hospitalized and is now improving. (sf.gov) The patient reported close contact with someone who had traveled internationally to an area where clade I mpox is circulating, according to the San Francisco Department of Public Health. City officials said exposure risk remains low for people outside higher-risk groups. (sf.gov) Mpox is a viral disease that usually spreads through close skin-to-skin contact and can cause fever, swollen lymph nodes, fatigue, and a rash that looks like pimples or blisters. The United States outbreak that began in 2022 was driven by clade II, while clade I is the strain tied to outbreaks in Central and Eastern Africa since 2023. (sf.gov) San Francisco has recorded 1,066 mpox cases since 2022 as of April 9, 2026, and city health officials said 24 residents were diagnosed with clade II mpox from January through March 2026. In prior years, the city usually saw fewer than 10 cases in the first quarter. (sf.gov) California health officials said this is the seventh identified clade I case in the state since November 2024, and they reported an average of 14.5 clade II cases a week in 2026, up from 5.8 in 2024 and 3.4 in 2025. Most recent infections have occurred in people who were unvaccinated. (goldrushcam.com) The vaccine in use, JYNNEOS, is a two-dose shot given 28 days apart, and the Centers for Disease Control and Prevention says both doses give the best protection. San Francisco and California officials said the same vaccine is expected to protect against both clade I and clade II. (cdc.gov) (cdph.ca.gov) Local guidance is aimed at people with higher exposure risk, including gay, bisexual, and other men who have sex with men, as well as some transgender and nonbinary people with similar sexual networks. San Francisco clinicians were told to check patients’ mpox risk and vaccination status at routine visits and to vaccinate travelers who may have sex with new partners or attend large events in places where clade I is circulating. (sf.gov) (cdc.gov) Health officials are also watching Europe, where San Francisco said locally acquired clade I cases have been increasingly reported, not just travel-linked infections. With summer travel and events approaching, the city is pushing eligible residents to finish the two-shot series now rather than wait for another spike. (sf.gov 1) (sf.gov 2)
