A clade I monkeypox virus (MPXV) outbreak is ongoing in the Democratic Republic of the Congo
travel-associated clade I MPXV infections have been reported in non-African countries. In November 2024, San Mateo County Health in California identified an electronic laboratory report of polymerase chain reaction results suggestive of clade I MPXV infection in a male traveler who had recently returned from East Africa. After conferring with the California Department of Public Health (CDPH), a county health department worker visited the patient that same day at his home and obtained skin pustule swab specimens for expedited clade I MPXV testing. Clade I MPXV was confirmed the following day by the CDPH Viral and Rickettsial Disease Laboratory. This was the first reported clade I MPXV infection in the Americas. Among 83 identified contacts, five received JYNNEOS vaccine as postexposure prophylaxis. All contacts were monitored for 21 days
no secondary cases were identified. Patients with mpox-compatible lesions or clinical features should receive MPXV testing, and health care providers should immediately notify public health authorities of suspected clade I MPXV infections (e.g., mpox manifestations and travel history to an area with ongoing clade I MPXV transmission) or upon receiving a nonvariola orthopoxvirus DNA detected, clade II MPXV DNA undetectable test result to trigger additional testing and facilitate the rapid implementation of transmission-based precautions and other preventive public health interventions.