San Francisco confirmed its first case of clade I mpox, the newer and potentially more severe strain circulating in eastern and central Africa since 2023. The San Francisco Department of Public Health announced that the city’s first clade I case was confirmed in a resident who had not received the mpox vaccine and was hospitalized but improving.
Clade I mpox has caused more than 53,000 cases among children and adults in Central and Eastern Africa, with at least 200 deaths. The CDC confirmed that until now, 15 cases of clade I mpox have been detected in the U.S. since late 2024, with over a quarter of these cases diagnosed in March 2026 alone. All U.S. cases were either in people who recently traveled to areas with outbreaks or, like the San Francisco case, were linked to travel.
The San Francisco patient reported close contact with another person who had traveled internationally. In other parts of the world, clade I has proven a more severe strain compared to clade II mpox, which caused an outbreak in the Bay Area in 2022. However, SFDPH officials are still determining whether clade I causes more severe disease than clade II in the U.S. The risk of exposure remains low for individuals not in higher-risk groups.
Vaccination and Symptoms
A two-dose vaccine offering protection against both clade I and clade II remains available for eligible people at higher risk. Mpox symptoms can include fever, chills, headache, muscle pain, and a painful rash with lesions appearing on many body parts, including the face, mouth, hands, feet, chest, genitals, and anus. The mpox virus spreads through close skin-to-skin contact with someone infected, including intimate physical contact and exposure to infected bodily fluids.
This article is an AI-assisted summary. All facts and figures are drawn from the original report: https://ww2.kqed.org/news/2026/04/16/mpox-clade-i-san-francisco-2026-symptoms-rash-where-to-find-monkeypox-vaccine/