The changing epidemiology of human monkeypox-A potential threat? A systematic review

PLoS Negl Trop Dis. 2022 Feb 11;16(2):e0010141. doi: 10.1371/journal.pntd.0010141. eCollection 2022 Feb.


Monkeypox, a zoonotic disease caused by an orthopoxvirus, results in a smallpox-like disease in humans. Since monkeypox in humans was initially diagnosed in 1970 in the Democratic Republic of the Congo (DRC), it has spread to other regions of Africa (primarily West and Central), and cases outside Africa have emerged in recent years. We conducted a systematic review of peer-reviewed and grey literature on how monkeypox epidemiology has evolved, with particular emphasis on the number of confirmed, probable, and/or possible cases, age at presentation, mortality, and geographical spread. The review is registered with PROSPERO (CRD42020208269). We identified 48 peer-reviewed articles and 18 grey literature sources for data extraction. The number of human monkeypox cases has been on the rise since the 1970s, with the most dramatic increases occurring in the DRC. The median age at presentation has increased from 4 (1970s) to 21 years (2010-2019). There was an overall case fatality rate of 8.7%, with a significant difference between clades-Central African 10.6% (95% CI: 8.4%- 13.3%) vs. West African 3.6% (95% CI: 1.7%- 6.8%). Since 2003, import- and travel-related spread outside of Africa has occasionally resulted in outbreaks. Interactions/activities with infected animals or individuals are risk behaviors associated with acquiring monkeypox. Our review shows an escalation of monkeypox cases, especially in the highly endemic DRC, a spread to other countries, and a growing median age from young children to young adults. These findings may be related to the cessation of smallpox vaccination, which provided some cross-protection against monkeypox, leading to increased human-to-human transmission. The appearance of outbreaks beyond Africa highlights the global relevance of the disease. Increased surveillance and detection of monkeypox cases are essential tools for understanding the continuously changing epidemiology of this resurging disease.

Publication types

  • Historical Article
  • Meta-Analysis
  • Research Support, Non-U.S. Gov't
  • Systematic Review

MeSH terms

  • Adolescent
  • Adult
  • Child
  • Child, Preschool
  • Democratic Republic of the Congo
  • Female
  • History, 20th Century
  • History, 21st Century
  • Humans
  • Male
  • Monkeypox virus / genetics
  • Monkeypox virus / physiology*
  • Mpox (monkeypox) / epidemiology*
  • Mpox (monkeypox) / history
  • Mpox (monkeypox) / mortality
  • Mpox (monkeypox) / virology
  • Travel-Related Illness
  • Young Adult

Grants and funding

This study was initiated and funded by Bavarian Nordic. The decision to publish the manuscript was made after the report of the paid systematic literature review by Pallas Health Research and Consultancy. The funder had a role in study design, data collection and analysis, decision to publish, and preparation of the manuscript. Baer PharMed Consulting, Ltd received funding for the development of the manuscript.