Rare Mpox Strain Detected In San Francisco
- Health officials report a spike in mpox cases across California, including a rare strain found in San Francisco. - The rare strain was identified for the first time in San Francisco amid rising statewide mpox numbers. - Officials urge Californians to get vaccinated to curb spread and protect vulnerable communities (patch.com).
San Francisco has confirmed its first case of clade I mpox, a rarer strain, in a resident who was hospitalized and is now improving. (sf.gov) The San Francisco Department of Public Health said the case was confirmed April 14, 2026, in an unvaccinated adult who reported close contact with someone who had traveled internationally. City officials announced the case on April 16. (sf.gov) California health officials said April 17 that the San Francisco infection was the state’s seventh identified clade I case since November 2024 and the first detected in the city. The state also said it is conducting enhanced surveillance and contact tracing. (cdph.ca.gov) Mpox is a virus that usually spreads through close skin-to-skin contact, including during sex, and both clade I and clade II can cause fever, swollen lymph nodes, fatigue and a rash that looks like pimples or blisters. The 2022 U.S. outbreak was caused by clade II, which still circulates at low levels in California. (sf.gov) State officials said California is averaging 14.5 clade II cases a week so far in 2026, up from 5.8 a week in the same period of 2024 and 3.4 in 2025. Most of those recent infections have occurred in people who were unvaccinated, according to the California Department of Public Health. (cdph.ca.gov) The Centers for Disease Control and Prevention said April 17 that the risk to most people in the United States remains low, even as clade I cases rise. The agency reported 16 U.S. clade I cases from November 2024 through mid-April 2026, including five reported since March 2026 that were not linked to each other. (cdc.gov) Federal health officials said clade I outbreaks tied to the current global surge have centered in Central and Eastern Africa, with newer outbreaks also reported in parts of Western Europe. KQED reported the San Francisco case made the city resident the 16th identified U.S. clade I patient. (cdc.gov) (kqed.org) San Francisco and California officials are urging people at higher risk to get both doses of the Jynneos vaccine, which they said protects against both clade I and clade II. The city said vaccine appointments are available through health care providers, pharmacies and local public health sites. (sf.gov) (cdph.ca.gov) For now, officials are treating the San Francisco case as a warning tied to travel and low vaccination, not as evidence of broad community spread. Their message has been consistent since April 16: risk to the general public is low, but people with exposure risk should get vaccinated before summer travel and large events. (sf.gov) (cdph.ca.gov)
