Deadlier Clade I Mpox Found Locally in California

Health officials confirmed three unrelated cases of clade I mpox in Los Angeles County and Long Beach — the first known local transmission of this more severe strain in the United States. All three patients, described as gay or bisexual men, were hospitalized and have since been discharged to isolate at home; none had recent travel to endemic regions and no epidemiologic links have been identified. Authorities are conducting contact tracing, genomic sequencing, targeted outreach and expanded testing amid concerns of person-to-person spread within sexual and social networks. Clade I historically causes more severe illness and higher mortality than clade II, with reports citing up to about 10% fatality in untreated cases, raising particular concern for people with weakened immune systems. Officials say overall public risk remains low but are urging vaccination for those at risk, close-contact precautions, rapid case investigation and vigilance to contain possible wider spread.