Mpox Cases Soar In CA As Rare Strain Detected For First Time In San Francisco

SAN FRANCISCO, CA — Health officials are sounding the alarm on Mpox cases quickly spreading in the San Francisco Bay Area, and their warnings come amid the first-ever detection of a more dangerous strain.

This month, the San Francisco Department of Public Health announced the first confirmed case of Clade I mpox in the city.

Local health officials said the Clade I mpox patient reported having close contact with another person who recently traveled internationally. The patient is in a hospital and expected to recover.

Last week's announcement marked the 7th confirmed case of Clade 1 mpox in California. Los Angeles County reported its first confirmed case of Clade 1 mpox in October.

In California, the weekly confirmed cases of Clade II mpox have more than doubled so far in 2026; there have been 14.5 weekly cases in 2026 compared to 5.8 in 2024 and 3.4 in 2025.

On Friday, state health officials said the rising mpox cases underscores the need for at-risk residents to get vaccinated.

"CDPH is closely monitoring mpox activity across California. While Clade I cases remain uncommon, Clade II mpox continues to circulate and we’re seeing rising cases," said Dr. Erica Pan, CDPH Director and State Public Health Officer. "This reinforces how important it is for people at higher risk to get both doses of the mpox vaccine. With summer travel and large events approaching, now is the ideal time to protect yourself if you or your sex partner may be at risk."

Mpox is an infection caused by the monkeypox virus, which is present in two variants: Clade I and Clade II. Both cause similar flu-like symptoms, but Clade I can lead to more severe symptoms and potentially require hospitalization. Both strains can be prevented by the same vaccine.

Clade I mpox has a mortality rate of between 1 and 10 percent. Clade II has a mortality rate of 4 to 6 percent, according to the CDC.

The Clade II variant is endemic to eastern and central Africa, where an outbreak has been attributed to more than 161,000 cases and killing more than 2,200 people over two years, but are now coming to halt, health experts say.

According to the CDC, Mpox Clade I and Clade II can be transmitted through personal contact by:

• Direct skin-to-skin contact with mpox rash or scabs from a person with mpox
• Contact with saliva, upper respiratory secretions (snot, mucus), and bodily fluids or lesions around the anus, rectum, or vagina from a person with mpox
• Pregnant women with monkeypox can pass the virus to the fetus during pregnancy or to the newborn during and after birth

The virus can also be spread by touching objects that have not been disinfected and through contact with infected animals.

More information on how to prevent the spread of mpox can be found on the California Department of Health website.