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Mpox strain that may be more severe appears to spread locally in U.S. for first time

By
Sara Moniuszko
Reporter, Lifestyle & Wellness
Sara Moniuszko is a health and lifestyle reporter at CBSNews.com. Previously, she wrote for USA Today, where she was selected to help launch the newspaper's wellness vertical. She now covers breaking and trending news for CBS News' HealthWatch.
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Sara Moniuszko

/ CBS News

The first U.S. cases of a potentially more severe form of mpox without known travel were reported in California, health officials said this week. 

Thursday, the Los Angeles County Department of Public Health confirmed an adult is now recovering at home after being hospitalized for a confirmed case of clade I mpox with no recent travel to areas the virus is typically found, primarily in parts of Africa. It was the second clade I case thought to be locally acquired, following a similar , also in L.A. County, earlier this week.

Compared to clade II mpox, which was the cause of the  and continued sporadic clusters in the United States, clade I mpox is more likely to cause , health officials say. Fatality rates for clade II range from less than 1% to 4% while rates for clade I range from 1% to 10%, according to . Clade II is also not generally seen in children, but clade I is being reported in more children in the Democratic Republic of the Congo.

At least six other cases of clade I mpox have been , including in , but they were identified in people who had recently traveled to affected areas in central and eastern Africa, the Centers for Disease Control and Prevention said. The strain also has been detected in  via wastewater testing.

"The identification of cases of clade I mpox, which may cause more severe illness than the more common clade II, is concerning," Los Angeles County Health Officer Dr. Muntu Davis said in a statement Thursday. "Mpox continues to be spread largely through close, intimate contact with symptomatic people, mainly during sexual activity."

The health department's release added the virus can be spread through "close person contact (sex, massage or cuddling) and within households or by sharing personal items."

While the risk to the general public remains low, officials are recommending certain groups, including gay, bisexual or other men who have sex with men, take preventative measures.

"Early detection, testing and vaccination are vital to controlling the spread of this virus," Davis said. "Getting both doses of the JYNNEOS vaccine provides the best protection against mpox."

Both clade I and clade II may present with flu-like symptoms followed by a rash, officials say. The CDC adds symptoms usually start within 21 days of exposure.

Johns Hopkins adds rashes for clade I tend to cover more of the body, including face and torso, while rashes from clade II do not always cover the body. 

Edited by Nicole Brown Chau

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