• Posted October 20, 2025

New, More Dangerous Mpox Strain Found in 3 Californians

A more dangerous strain of mpox, a virus that causes painful lesions and flulike symptoms, has been detected in three California residents who had not traveled internationally.

Officials said this is the first known local spread of the severe form in the United States.

The strain, called Clade 1, has caused tens of thousands of infections and hundreds of deaths in central and eastern Africa. Until now, it had never spread from person to person inside the U.S., The New York Times reported.

A milder strain, Clade 2, was responsible for the 2022 mpox outbreak that sickened about 30,000 Americans and continues to circulate at low levels. However, some cities, including Los Angeles, have reported an uptick in cases, with 118 infections confirmed in 2025.

California officials said the new Clade 1 cases were found in one person in Long Beach and two in Los Angeles. All three were hospitalized and have since been discharged to recover at home in isolation. No link among the cases has been identified.

“It’s still too early to tell, but we’re concerned there will be more severe disease,” Dr. Sonali Kulkarni of the Los Angeles County Department of Public Health told The Times. 

The patients were described as gay and bisexual men, a group that remains at higher risk of mpox infection. While mpox is not classified as a sexually transmitted infection, it can spread through close or intimate contact, shared items or ongoing household exposure.

Dr. Kelly Johnson, an infectious disease specialist at the University of California, San Francisco, said that while the overall risk to the public remains low, people should remain alert. 

“My concern is that person-to-person, community spread could be ongoing,” she said.

Symptoms of mpox are flulike: Fever, fatigue, headache and a rash that can lead to painful lesions. 

The virus can incubate for up to three weeks before symptoms appear, meaning people can unknowingly spread it to others around them.

The U.S. Centers for Disease Control and Prevention (CDC) recommends vaccination for people at higher risk, like those with multiple sexual partners or underlying health conditions such as untreated HIV. Two doses of the Jynneos vaccine are highly effective at preventing severe illness.

The only previous U.S. case of Clade 1 mpox occurred last year, when a California resident who had recently traveled to East Africa was infected but did not spread the virus.

Public health experts warned that recent cuts to federal and global health programs could hinder outbreak containment.

“The infrastructure we built during the 2022 outbreak has just been eviscerated,” Joseph Osmundson, a clinical associate professor of biology at New York University, told The Times. “The very things we need to understand if we have a problem now, and if we will have a problem in the future, are being systematically dismantled.”

More information

The Cleveland Clinic has more on mpox.

SOURCE: The New York Times, Oct. 17, 2025