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

• Published in: PLoS neglected tropical diseases Vol. 16; no. 2; p. e0010141
• Main Authors: Bunge, Eveline M., Hoet, Bernard, Chen, Liddy, Lienert, Florian, Weidenthaler, Heinz, Baer, Lorraine R., Steffen, Robert
• Format: Journal Article
• Language: English
• Published: United States Public Library of Science 01.02.2022; Public Library of Science (PLoS)
• Subjects: Adolescent; Adult; Adults; Age; Biology and Life Sciences; Causes of; Child; Child, Preschool; Children; Cross-protection; Democratic Republic of the Congo; Development and progression; Disease transmission; Diseases; Distribution; Epidemics; Epidemiology; Fatalities; Female; Grey literature; History, 20th Century; History, 21st Century; Human monkeypox; Humans; Immunization; Male; Medical Subject Headings-MeSH; Medicine and Health Sciences; Monkeypox; Monkeypox virus - genetics; Monkeypox virus - physiology; Mpox; Mpox (monkeypox) - epidemiology; Mpox (monkeypox) - history; Mpox (monkeypox) - mortality; Mpox (monkeypox) - virology; Orthopoxvirus; Outbreaks; People and Places; Research and Analysis Methods; Risk taking; Smallpox; Systematic review; Transmission; Travel-Related Illness; Tropical diseases; Vaccination; Vaccines; Viral infections; Young Adult; Young adults; Zoonoses; Democratic Republic of the Congo; Africa; Liberia; Gabon; Cameroon; United Kingdom > UK; South Sudan; United States > US; Sudan; Sierra Leone; Nigeria
• ISSN: 1935-2735; 1935-2727; 1935-2735
• DOI: 10.1371/journal.pntd.0010141

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.