Health officials have confirmed three cases of a new, more dangerous strain of mpox in California, raising concerns about its higher transmissibility and potential for severe illness. The new variant appears to spread faster and may cause more intense symptoms, including fever, swollen lymph nodes, painful rash, and lesions.
An extremely dangerous strain of mpox virus that leads to painful lesions and flu-like symptoms has been detected in three people in California who did not travel abroad. According to health officials, this is the first known local spread of the severe form in the United States.
The strain – clade 1 has caused tens of thousands of infections and hundreds of deaths in central and eastern Africa. Officials said till now, it had never spread from one person to another inside the US. However, a relatively milder strain – Clade 2, was responsible for the 2022 mpox outbreak that infected more than 30,000 Americans and continues to circulate at low levels. A few cities in California – including Los Angeles, have reported an uptick in cases, with 118 infections confirmed in 2025.
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 and are currently recovering at home. Authorities said all the three cases were unrelated. “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.
Three patients are bisexual
According to the doctors treating the patients, all three are gay and bisexual men – a group that remains at higher risk of mpox infection. Even though it is not classified as a sexually transmitted infection – doctors say mpox spreads through close or intimate contact, shared items or ongoing household exposure.
Doctors say even though the overall risk to the public remains low, everyone should be alert as the person-to-person community spread can be happening.
The only previous US 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.
What is mpox?
Mpox, previously known as monkeypox, is a flu-like disease caused by a virus that causes rashes all over the body. The infection spreads with the Orthopoxvirus monkeypox virus with small pieces of genetic information in a protective coating. Doctors say the rash is similar to the one caused by a related virus, smallpox. Cases of mpox happen regularly in parts of Africa, where it is endemic. However, outbreaks do sometimes happen in other places around the world. There are two known subtypes of mpox:
- Clade 1 which is endemic to Central Africa and causes more serious illness than clade 2.
- Clade 2 is endemic to East Africa. There’s been a global outbreak of clade II mpox since 2022.
Signs and symptoms of mpox
A few signs and symptoms of mpox include:
- Rashes, skin ulcers, and blisters
- High fever
- Swollen lymph nodes
- Chills
- Headaches
- Muscle aches
- Fatigue and tiredness
