The emergence of Clade IIb and Ib mpox viruses: a state-of-the-art review

Abstract

Mpox, a zoonotic Orthopoxvirus infection, was historically endemic to West and Central Africa. In 2022, it sparked a significant global outbreak, raising concerns about its spread beyond traditional regions. Notably, the emergence of Clade IIb and Ib strains has alarmed the global health community due to their increased transmission among humans. This paper examines mpox viruses and their general characteristics, their evolution, and the emergence of novel clades with unique features. Clade IIb stands out for its unique genetic mutations, which may enhance its transmissibility. Clinically, infections often present with fewer anogenital lesions and milder symptoms, which can complicate diagnosis. PCR testing remains the most reliable diagnostic tool, although emerging point-of-care tests show promise. Treatments such as tecovirimat and immune-based therapies (e.g., VIGIV) have demonstrated success, despite limitations. The MVA vaccine provides partial protection, although its efficacy against Clade IIb requires further validation. The emergence of Clades IIb and Ib, with distinct transmission dynamics, especially among specific population groups, underscores the need for targeted public health responses. This review highlights critical surveillance challenges in endemic African regions, where underreporting and limited diagnostic infrastructure hinder early detection. By analyzing the evolution and spread of newer clades, this review provides unique insights into mpox's shifting epidemiology and outlines implications for global preparedness, including the urgent need for strengthened surveillance systems, equitable access to vaccines, and coordinated international efforts focusing on research and preparedness to help mitigate future risks.