Mpox

Mpox (formerly known as monkeypox) is a zoonotic viral disease caused by the monkeypox virus (MPXV), an Orthopoxvirus belonging to Poxviridae family. The virus comprises two major clades: clade I, predominantly detected in Central and East Africa, and clade II, historically associated with West Africa and more recent global transmission. The multinational outbreak that emerged in 2022 was primarily driven by clade IIb.

In response to the rapid international spread, the World Health Organization (WHO) declared mpox a Public Health Emergency of International Concern (PHEIC) in July 2022. A subsequent surge in clade I infections in Central Africa, with the emergence of a new clade Ib, prompted a redeclaration of the PHEIC in August 2024. In September 2025, following sustained declines in reported cases across affected countries in Central and East Africa, the WHO announced that mpox no longer constituted a PHEIC. This announcement marked a transition from the acute emergency phase to the incorporation of mpox prevention, surveillance, and control into long-term public health programmes.

As of 2025, mpox transmission remains a public health concern, particularly in the African Region, where several countries continue to report active outbreaks. While overall case trends are declining, cross-border transmission, surveillance gaps, and recurrent outbreaks underscore the need for continued vigilance.

Clinically, mpox is generally a self-limiting illness in immunocompetent individuals, typically presenting with fever, lymphadenopathy, and a vesiculopustular rash. However, severe disease may occur in children and immunocompromised individuals, emphasizing the importance of sustained access to diagnostics, clinical management, vaccination, and community-based prevention measures.

For up-to-date information on mpox, please consult the WHO Blueprint website: Blueprint

Biological products for Mpox

Biological products used to contain mpox outbreaks include a third-generation attenuated vaccinia-based vaccine, authorized under the product names Imvanex (EU), Jynneos (USA), and Imvamune (Canada), which was prequalified by WHO in 2024. In addition, approximately 20 mpox vaccine candidates using mRNA, DNA, and live-attenuated platforms are in development, most targeting conserved MPXV intracellular mature virion (MV) and extracellular envelope virion (EV) antigens. Clinical-stage products include two quadrivalent mRNA vaccines, BioNTech’s BNT-166 and Moderna mRNA-1769. Therapeutic options currently rely on smallpox antivirals and Vaccinia Immunoglobulins (VIGIV) used off-label, while several monoclonal antibody candidates are progressing through early development.

Mpox Measurement standards

WHO International Standards (ISs) serve as the highest order of reference materials for calibrating assays worldwide, supporting harmonization and improving the comparability of results across different methods measuring biological activity.

The WHO Expert Committee on Biological Standardization (ECBS) has endorsed the development of International Standards for mpox, and the following projects are currently in progress:

• The first WHO international standards for  anti-Mpox antibodies
• The first WHO international standards for anti-Vaccinia virus antibodies
• The WHO reference reagents for Mpox DNA for Nucleic acids testing

The WHO Collaborating Centre for biological standardization, the Medicines and Healthcare products Regulatory Agency UK, is leading the projects with the support of other WHO Collaborating Centers and worldwide laboratories. The standards will be available through the nibsc.org website.