San Francisco Reports First Clade I Mpox Case

San Francisco health officials confirmed the city’s first case of clade I mpox on April 14, 2026, marking the 16th such case detected in the United States since late 2024. The case involved an unvaccinated adult who was hospitalized but is now improving. The individual reported close contact with someone who had traveled internationally, according to the San Francisco Department of Public Health.

Clade I mpox is a variant of the virus formerly known as monkeypox that has been circulating in eastern and central Africa since 2023, where it has caused more than 53,000 cases and at least 200 deaths among children and adults. Health officials note that while both clade I and clade II mpox cause similar symptoms—including flu-like signs such as fever, swollen lymph nodes, or fatigue, followed by a rash resembling pimples or blisters—clade I is considered potentially more severe.

The Centers for Disease Control and Prevention reported that until the San Francisco case, 15 cases of clade I mpox had been detected in the U.S. Since late 2024, with over a quarter of those diagnosed in March 2026 alone. All U.S. Cases to date have occurred in individuals with recent travel to areas associated with the outbreak in Central and Eastern Africa or parts of Western Europe with recent outbreaks, or through close contact with someone who had such travel history.