Emerging Mpox Strain Detected In Bay Area, Marking Nation's 1st Reported Case

SAN MATEO COUNTY, CA — The nation's first-known case of a more aggressive strain of mpox was detected in California, officials said Saturday.

A patient was treated for clade I mpox in San Mateo County, according to the California Department of Public Health (CDPH). They are isolating at home and recovering.

The person had recently traveled to Africa, which is experiencing an outbreak of clade I mpox in the continent's central and eastern regions.

There is no concern or evidence that the strain is spreading in California or the United States, the CDPH said.

Public health workers are contacting people who had close contact with the patient.

The clade I strain differs from clade II mpox, which has been circulating around the nation since 2022. Clade I mpox has caused more-severe illness than clade II. But recent infections suggest that it may not be as severe as in previous outbreaks, especially for patients who can access quality medical care, the CDPH said.

Common symptoms of mpox include skin rashes and lesions accompanied by fever, headache, muscle aches and low energy.

Mpox spreads through close or intimate contact, which could mean living together, skin-to-skin touch or sexual activity. It can also be spread by touching contaminated items and surfaces.