By Christian Leonard, San Francisco Chronicle The Tribune Content Agency

San Mateo County health officials said a traveler has tested positive for a new strain of mpox, the first such case confirmed in the United States.

The person is isolating at home and recovering with mild symptoms, officials said Saturday, adding that there is no evidence the new strain is spreading in San Mateo County or anywhere else in the United States. Officials also said the patient had been exposed to the virus while traveling to Africa, where there is an outbreak of the new strain in the central and eastern regions of the continent.

The patient was treated in San Mateo County, though health officials did not specify whether the person is a resident.

A global outbreak of the clade II mpox variant caused the World Health Organization to declare a public health emergency in 2022. Spread primarily through skin-to-skin contact, including intimate and sexual activity, mpox's symptoms commonly include rashes or lesions. Spread of the virus in the U.S. slowed quickly as access to vaccines and medication expanded.

The current outbreak is driven by the clade I mpox variant, which health officials say appears to cause more severe illness than the clade II variant, killing more than 1,000 people in the Democratic Republic of the Congo alone this year. Officials also said risk of exposure to both variants in the U.S. remains low, though they recommend some groups - including men who have sex with men - get vaccinated against mpox.

Reach Christian Leonard: [email protected]