LA County confirms second US case of more severe mpox strain not linked to travel

The first two cases in the U.S. of a more severe strain of mpox not linked to travel have been confirmed in L.A. County.

On Thursday, the L.A. County Department of Public Health confirmed a case of clade I mpox in an adult who officials say was hospitalized and now is recovering at home. Earlier this week, Long Beach, which has its own public health department, confirmed a separate case — also without recent travel history.

While there have been other cases of the clade I illness nationally, these are the first without known travel to regions where the virus usually is found. The strain had been linked to outbreaks in some African countries since 2024, officials said.

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"The identification of cases of clade I mpox, which may cause more severe illness than the more common clade II, is concerning," said Muntu Davis, L.A. County’s health officer.

While clade II causes mild to moderate illness, clade I may be more severe and can spread more easily, officials said. Both strains are spread through close personal contact, like touching a lesion or sex, and by sharing personal items. Symptoms include lesions, rash, fever and body aches.

Officials are urging people who may be at higher risk to get vaccinated, including men who have sex with men, people who are immunocompromised and those planning to travel to places with ongoing mpox outbreaks. If you have symptoms, officials say you should contact your medical provider and get tested.

So far in 2025, there have been 118 cases of the less severe, clade II mpox reported in L.A. County. Last year, the county reported a total of 220 cases with a sharp uptick in cases reported during the fall.