Rare Mpox Strain Detected In San Francisco
- Health officials reported a rare mpox strain has been detected in San Francisco as statewide cases surge. - Authorities are urging Californians to get vaccinated to curb spread and protect vulnerable populations, officials said. - Public health agencies are monitoring variants and increasing outreach and vaccination efforts (patch.com).
San Francisco has detected its first clade I mpox case, a rarer strain that California officials say emerged as statewide mpox cases climbed in 2026. (sf.gov) The San Francisco Department of Public Health said April 16 that the case was confirmed April 14 in an unvaccinated adult who was hospitalized and is improving. The patient reported close contact with someone who had traveled internationally. (sf.gov) California’s health department said April 17 that this was the seventh identified clade I case in California since November 2024 and the first in San Francisco. State officials said they are doing enhanced surveillance and contact tracing to look for additional cases. (cdph.ca.gov) Mpox spreads mainly through close skin-to-skin contact, including sex, and both clade I and clade II can cause fever, swollen lymph nodes, fatigue and a rash that looks like pimples or blisters. San Francisco officials said the 2022 U.S. outbreak was caused by clade II, while clade I cases in the United States remain rare. (sf.gov) State officials said California is averaging 14.5 clade II cases a week in 2026, up from 5.8 in 2024 and 3.4 in 2025. They said most of those infections have occurred in people who were unvaccinated. (cdph.ca.gov) The Centers for Disease Control and Prevention said most U.S. mpox cases are still clade II and continue to occur in people who are unvaccinated or who received only one dose of JYNNEOS. The agency recommends two doses for maximum protection. (cdc.gov) KQED reported that the San Francisco patient is the 16th clade I case identified in the United States so far. It also reported that more than a quarter of those U.S. clade I cases were diagnosed in March 2026 alone. (kqed.org) California and San Francisco officials said the risk to the general public remains low, but they are urging people at higher risk to complete the two-dose vaccine series before summer travel and large events. San Francisco said vaccine appointments are available through health care providers, pharmacies and city-listed clinics. (cdph.ca.gov, sf.gov)
