The first reported case of monkeypox virus clade Ⅰb infection in china-clinical presentation and epidemiologic implications.

Recently, Monkeypox Virus (MPXV) clade Ib has caused serious health hazards in several countries. Herein, we report the first case of a clade Ib MPXV infection in China. MPXV was detected in a 28-year-old female on January 2, 2025. Whole-genome sequencing analysis revealed the strain to be clade Ib. The case presented with headache and disseminated rashes, with symptoms resolving symptomatic treatment and scabs shedding prior to discharge. Epidemiological studies and laboratory tests suggested transmission through close contact with a man who recently came from the Democratic Republic of Congo. Significantly, although some environmental samples tested positive, all contacts reminded negative, indicating that absence of secondary transmission. Furthermore, the clinical presentation of this case showed different manifestations from clade IIb MPXV infections. Epidemiological patterns also suggested sexual transmission served as the predominant route for clade Ib MPXV spread. These findings provide critical insights to enhance early detection strategies and inform targeted intervention measures aimed at curbing disease progression while mitigating risks of wider community spread.