First Clade Ib Monkeypox Virus Infection Reported in the Americas - California, November 2024

Abstract

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.

FIGURE 1

Signs and symptoms; clinical evaluation, findings, and management; and laboratory results in a case of clade Ib monkeypox virus infection in a traveler to East Africa — California, 2024 Abbreviations: ED = emergency department; MPXV = monkeypox virus; NVO = nonvariola orthopoxvirus; PCR = polymerase chain reaction. * Patient received oral antibiotics on two separate occasions, beginning on days 2–3, and again after hospital discharge on days 6–11. Intravenous antibiotics were administered during the patient’s hospitalization. ^† The patient’s travel to East Africa was ascertained at the time of the ED evaluation on day 7. Swabs were sent for testing at that time.

FIGURE 2

Progression of lesions in a patient with clade Ib monkeypox virus infection 7, 11, and 23 days after return to the United States from East Africa — California, 2024 Photos/Anna Branzuela (photos reproduced with the patient’s permission) Abbreviations: ED = emergency department; MPXV = monkeypox virus.