Epidemiology

Mpox epidemiology in human populations

MPXV is spread through close physical contact. Patterns of transmission, and populations affected, differ by MPXV clade and subclade.

Thematic leads

Thematic lead 1

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Thematic lead 2

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Contact the thematic leads

Epidemiology knowledge gaps

Primary knowledge gaps identified in the Mpox R&D Roadmap 2026:

Disease burden

What is the true mpox disease burden and how is it distributed?

Transmission dynamics

What are the key drivers of sustained human-to-human transmission in different clinical and non-clinical settings?

Viral evolution and adaptation

How is MPXV evolving in human populations?

Functional consequences

What are the implications of MPXV evolution?

Data for action

How can epidemiological data best be delivered to policymakers to inform disease control and decision-making?

Epidemiology workplan

A CORC workplan for the epidemiology theme is in development.

Epidemiology background

Mpox was largely restricted to sub-Saharan Africa until 2003, when cases of human mpox associated with animals imported from West Africa were reported in the USA. In 2017, Nigeria witnessed a resurgence of mpox, 38 years after the last case was reported in 1978. Following this outbreak, subsequent travel-related exportations of mpox from Nigeria to several countries occurred between 2018 and 2021.

In May 2022, sustained transmission of clade IIb MPXV was reported on a global scale within dense sexual networks, which was followed by unprecedented expansion of clade Ib, marked by sustained human-to-human transmission within Africa. Genomic investigations of the 2022 global outbreak revealed signs of microevolution compared to earlier reference genomes. Notably, mutation patterns consistent with host APOBEC3-mediated editing have been reported13, highlighting the potential for viral adaptation, altered transmissibility and antigenicity, and possible impacts on diagnostics and immune escape.

The recent detection of inter-clade recombinant viruses (Ib/IIb) in the UK and India in 2025 and 2026 highlights other potential mechanisms of evolution and further complicates diagnostic interpretation[1]. WHO has highlighted the presence of genomic mosaicism in these inter-clade recombinant strains, raising concerns about their potential wider circulation[2].

[1] Pullan ST, Everall I, Doherty R et al. Inter-Clade Recombinant Mpox Virus Detected in England in a Traveller Recently Returned from Asia. December 2025. Available at: https://virological.org/t/inter-clade-recombinant-mpox-virus-detected-in-england-in-a-traveller-recently-returned-from-asia/1015.

[2] WHO. Mpox: recombinant virus with genomic elements of clades Ib and IIb – Global. 14 February 2026. Available at: https://www.who.int/emergencies/disease-outbreak-news/item/2026-DON595

Surveillance

These events have highlighted gaps in surveillance, diagnostics and outbreak preparedness. Thus, robust research on MPXV evolution is critical for detecting functionally relevant genomic changes and for interpreting phylogenetic signals detected in outbreak investigations. Although some genomic characterisation is occurring, genomic surveillance is not yet being systematically applied to MPXV in low-resource/high-burden settings.

Research on mpox epidemiology and virus evolution is important for historically endemic regions and for the broader global community. In non-endemic settings, timely epidemiological and genomic data enable rapid case detection, contact tracing, and targeted public health interventions that limit onward spread; in historically endemic countries, longitudinal surveillance is required to characterise animal reservoirs, spillover dynamics and the drivers of sustained human-to-human transmission.

Knowledge from epidemiological and evolutionary studies will directly improve detection and response by:

Enabling earlier identification of transmission chains and geographic spread through genomic and case-based surveillance.
Informing refinement of diagnostics and genomic assays to maintain sensitivity and specificity in the face of viral evolution.
Guiding vaccine and therapeutic strategies through better characterisation of antigenic and phenotypic variation.
Supporting evidence-based public health policies and risk communication tailored to both endemic and non-endemic contexts.

Therefore, sustained investment in laboratory capacity, data sharing and integrated One Health surveillance, particularly in historically endemic countries, is essential to strengthen global mpox preparedness and control.

Further, sustained MPXV transmission within particular social and sexual networks, including historically stigmatised populations, has highlighted the need for equitable, stigma-free public health strategies that ensure access to prevention and care for marginalised populations[1].

[1] Wannigama DL, Amarasiri M, Phattharapornjaroen P et al. Community-based mpox and sexually transmitted disease surveillance using discarded condoms in the global south. Lancet Infect Dis. 2024;24(10):e610-e613. doi: 10.1016/S1473-3099(24)00514-0.