CDC official travel advisories or announcements

First U.S. Case of Severe Clade I Mpox Confirmed in San Mateo County, California

Nov 16, 2024, 10:16 PM

U.S. health officials have confirmed the country's first known case of Clade I mpox, a more severe strain of the virus, in a resident of San Mateo County, California. The individual recently returned from Eastern Africa and is isolating at home with improving symptoms without treatment. Clade I mpox, which has been circulating in Central and Eastern Africa, is considered more severe than the Clade IIb strain responsible for the global outbreak that began in 2022. The California Department of Public Health and the Centers for Disease Control and Prevention (CDC) are conducting further testing and are monitoring the situation. The CDC is awaiting the specimen for confirmation testing and is assisting state and local partners to understand more about this case. Health officials emphasize that there is no evidence of local transmission and that the risk to the public remains low.