Health officials on Saturday said they have identified the first U.S. case of an mpox strain that has recently prompted global health alerts over concerns about its spread, severity and transmissibility.

The first case in the U.S. of a more severe strain of mpox was reported in San Mateo County, the California Department of Public Health said.

The United States confirmed its first case of clade I mpox, a more aggressive strain, the US Centers for Disease Control and Prevention announced.