Health officials have confirmed Los Angeles County’s first case of the more severe clade I mpox strain in an adult who had not recently traveled to areas where the virus typically circulates.

The Los Angeles County Department of Public Health said the individual was hospitalized but is now recovering at home. It’s the second clade I mpox case in the county and the second in the nation involving someone without known international travel. The City of Long Beach, which operates its own health department, reported a separate case earlier this week.

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County officials said they are working with the California Department of Public Health and the U.S. Centers for Disease Control and Prevention to investigate the infections, conduct contact tracing and prevent further spread.

Mpox, previously known as monkeypox, has two main strains — clade I and clade II. The clade II strain, which causes milder illness, has been circulating in the U.S. since 2022. The clade I strain is considered potentially more severe and has been linked to outbreaks in parts of Africa.

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Both strains can cause flu-like symptoms followed by a rash and spread through close contact, including sex, cuddling or sharing personal items.

"The identification of cases of clade I mpox, which may cause more severe illness than the more common clade II, is concerning," said Dr. Muntu Davis, the county’s health officer. "Early detection, testing and vaccination are vital to controlling the spread of this virus."

The JYNNEOS vaccine is a two-dose shot that protects against both strains.