Epidemiology (References)

25 July 2022

Yang ZS, Lin CY, Urbina AN, et al. The first monkeypox virus infection detected in Taiwan-the awareness and preparation. Int J Infect Dis. 2022 Jul 25:S1201-9712(22)00445-3. PubMed: https://pubmed.gov/35902024. Full text: https://doi.org/10.1016/j.ijid.2022.07.051

“On the 16th of June, a 20-year-old young man who has studying in Germany, during January to June 2022, returned to Taiwan. After four days, he developed symptoms that included fever, sore throat, muscle pain, lymph node swelling in the groin, and a skin rash.”


9 July 2022

Selb R, Werber D, Falkenhorst G, et al. A shift from travel-associated cases to autochthonous transmission with Berlin as epicentre of the monkeypox outbreak in Germany, May to June 2022. Euro Surveill. 2022 Jul;27(27). PubMed: https://pubmed.gov/35801518. Full text: https://doi.org/10.2807/1560-7917.ES.2022.27.27.2200499

In early July 2022, Germany has one of the highest overall number of monkeypox (MPX) cases in Europe. The authors describe the epidemiology of MPX in Germany and the shift from travel-associated to autochthonous transmission in Berlin, often in association with visits to clubs and parties.  (Berlin is the epicenter of the outbreak in Germany with 69% of all cases.) Median age: 38 years (IQR: 32-44). Hospitalization status was reported for 455 cases of which 38 cases (8%) were admitted to hospital.


8 July 2022

Iñigo Martínez J, Gil Montalbán E, Jiménez Bueno S, et al. Monkeypox outbreak predominantly affecting men who have sex with men, Madrid, Spain, 26 April to 16 June 2022. Euro Surveill. 2022 Jul;27(27). PubMed: https://pubmed.gov/35801519. Full text: https://doi.org/10.2807/1560-7917.ES.2022.27.27.2200471

Iñigo Martínez et al. report 508 confirmed cases of monkeypox (MPX) in the Madrid region of Spain, 503 (99%) of whom were men. Median age was 35 years (range: 18-67). 427 cases (84.1%) reported condomless sex or sex with multiple partners (predominantly MSM) within the 21 days before onset of symptoms. The authors hypothesize that both the location of the rash, mainly in the anogenital and perineal area, as well as the presence of inguinal lymphadenopathy, might suggest that close physical contact during sexual activity played a key role in transmission. They recommend to actively work with LGBTIQ+ groups to adopt preventive measures.


1 July 2022

Anwar F, Waris A. Monkeypox virus outbreak: a brief timeline. New Microbes New Infect. 2022 Jul 1;48:101004. PubMed: https://pubmed.gov/35928519. Full text: https://doi.org/10.1016/j.nmni.2022.101004

A brief timeline.


23 June 2022

Haddad N. The presumed receptivity and susceptibility to monkeypox of European animal species. Infect Dis Now. 2022 Jun 23:S2666-9919(22)00122-1. PubMed: https://pubmed.gov/35753629. Full text: https://doi.org/10.1016/j.idnow.2022.06.006

“The sizable present-day number of human excreters during the clinical phase (3 weeks maximum) raises the question of a risk in our [European] countries of animals being contaminated by infected humans (reverse zoonosis). As regards dogs and ferrets, no data are available, and they are not known to be infected by Poxviridae. On the other hand, cats as well as cows are susceptible to Cowpox, another zoonotic Orthopoxvirus, which they transmit to humans. One study has demonstrated the pronounced susceptibility of the adult albino rabbit.”


23 June 2022

Bisanzio D, Reithinger R. Projected burden and duration of the 2022 Monkeypox outbreaks in non-endemic countries. Lancet Microbe. 2022 Jun 23:S2666-5247(22)00183-5. PubMed: https://pubmed.gov/35753315. Full text: https://doi.org/10.1016/S2666-5247(22)00183-5

Using an individual-based mathematical modelling framework, the authors find that the introduction of people with monkeypox could lead to small national outbreaks of moderate duration and that, ultimately, the outbreaks would all subside. Their model would also suggest that “a strong public health response—specifically contact tracing and surveillance, isolation of symptomatic cases, and ring vaccination—would substantially reduce the number of secondary cases by up to 86·1% and duration of the outbreak by up to 75·7%.”


17 June 2022

Cohen J. Monkeypox could establish new reservoirs in animals. Science. 2022 Jun 17;376(6599):1258-1259. PubMed: https://pubmed.gov/35709274. Full text: https://doi.org/10.1126/science.add4868

“As this outbreak of monkeypox expands, the virus has an unprecedented opportunity to establish itself in non-African species, which could infect humans and provide greater opportunity for more dangerous variants to evolve.” People infected with MPXV should avoid contact with their pets.


15 June 2022

Pan D, Sze S, Nazareth J, et al. Monkeypox in the UK: arguments for a broader case definition. Lancet. 2022 Jun 25;399(10344):2345-2346. PubMed: https://pubmed.gov/35716671. Full text: https://doi.org/10.1016/S0140-6736(22)01101-1

The authors propose that “probable case definitions of monkeypox be broadened to include anyone with an unexplained vesiculo-pustular rash on any part of their body with associated prodrome of fever, malaise, and lymphadenopathy so that fewer cases are missed in the community.”


10 June 2022

Minhaj FS, Ogale YP, Whitehill F, et al. Monkeypox Outbreak – Nine States, May 2022. MMWR Morb Mortal Wkly Rep. 2022 Jun 10;71(23):764-769. PubMed: https://pubmed.gov/35679181. Full text: https://doi.org/10.15585/mmwr.mm7123e1

“The high proportion of initial cases diagnosed in this outbreak in persons who identify as gay, bisexual, or other MSM, might simply reflect an early introduction of monkeypox into interconnected social networks; this finding might also reflect ascertainment bias because of strong, established relationships between some MSM and clinical providers with robust STI services and broad knowledge of infectious diseases, including uncommon conditions.”


4 June 2022

Perez Duque M, Ribeiro S, Martins JV, et al. Ongoing monkeypox virus outbreak, Portugal, 29 April to 23 May 2022. Euro Surveill. 2022 Jun;27(22):2200424. PubMed: https://pubmed.gov/35656830. Full text: https://doi.org/10.2807/1560-7917.ES.2022.27.22.2200424

The authors describe describe the preliminary results of an outbreak investigation in Portugal and the epidemiological characteristics of 27 confirmed cases. Their data would suggest that undetected spread of MXPV might have occurred in Europe at least since early April.


4 June 2022

Vivancos R, Anderson C, Blomquist P, et al. Community transmission of monkeypox in the United Kingdom, April to May 2022. Euro Surveill. 2022 Jun;27(22):2200422. PubMed: https://pubmed.gov/35656834. Full text: https://doi.org/10.2807/1560-7917.ES.2022.27.22.2200422

The authors describe the first sustained transmission of monkeypox virus infection  in the UK with evidence of human-to-human transmission through close contact, including in sexual networks. They conclude that “the current outbreak signals a change in basic assumptions about the epidemiology of MPXV in Europe with profound implications for surveillance and control.”


1 June 2022

Haider N, Guitian J, Simons D, et al. Increased outbreaks of monkeypox highlight gaps in actual disease burden in Sub-Saharan Africa and in animal reservoirs. Int J Infect Dis. 2022 May 29;122:107-111. PubMed: https://pubmed.gov/35640830. Full text: https://doi.org/10.1016/j.ijid.2022.05.058

Conclusion: “The 2022 European, American and Australian clusters of MPX cases are possibly results of importation of MPXV from West Africa where an increased transmission is facilitated by multiple factors including increased synanthropic rodent population, or species composition, and adaptation of rodents to human settings and declining population immunity from smallpox vaccines. The global spreading was possibly facilitated by the mass gathering of a pride festival celebrated in Europe in early May.”


19 April 2022

Mauldin MR, McCollum AM, Nakazawa YJ, et al. Exportation of Monkeypox Virus From the African Continent. J Infect Dis. 2022 Apr 19;225(8):1367-1376. PubMed: https://pubmed.gov/32880628. Full text: https://doi.org/10.1093/infdis/jiaa559

“Four individuals traveling from Nigeria to the United Kingdom (n = 2), Israel (n = 1), and Singapore (n = 1) became the first human monkeypox cases exported from Africa, and a related nosocomial transmission event in the United Kingdom became the first confirmed human-to-human monkeypox transmission event outside of Africa.”


11 February 2022

Bunge EM, Hoet B, Chen L, et al. The changing epidemiology of human monkeypox-A potential threat? A systematic review. PLoS Negl Trop Dis. 2022 Feb 11;16(2):e0010141. PubMed: https://pubmed.gov/35148313. Full text: https://doi.org/10.1371/journal.pntd.0010141

A prescient paper, only a few months before the European outbreak in May 2022: “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.”


22 September 2021

Diaz JH. The Disease Ecology, Epidemiology, Clinical Manifestations, Management, Prevention, and Control of Increasing Human Infections with Animal Orthopoxviruses. Wilderness Environ Med. 2021 Dec;32(4):528-536. PubMed: https://pubmed.gov/34563454. Full text: https://doi.org/10.1016/j.wem.2021.08.003

“Zoonotic orthopoxvirus outbreaks have occurred repeatedly worldwide, including monkeypox in Africa and the United States, cowpox in Europe, camelpox in the Middle East and India, buffalopox in India, vaccinia in South America, and novel emerging orthopoxvirus infections in the United States, Europe, Asia, and South America. Waning smallpox immunity may increase the potential for animal-to-human transmission followed by further community transmission person-to-person (as demonstrated by monkeypox and buffalopox outbreaks) and by contact with fomites (as demonstrated by camelpox, cowpox, and, possibly, Alaskapox).”


24 March 2021

Nguyen PY, Ajisegiri WS, Costantino V, Chughtai AA, MacIntyre CR. Reemergence of Human Monkeypox and Declining Population Immunity in the Context of Urbanization, Nigeria, 2017-2020. Emerg Infect Dis. 2021 Apr;27(4):1007-14. PubMed: https://pubmed.gov/33756100. Full text: https://doi.org/10.3201/eid2704.203569

“The substantial resurgence of monkeypox in Nigeria in 2017 appears to have been driven by a combination of population growth, accumulation of unvaccinated cohorts, and decline in smallpox vaccine immunity.”


30 December 2020

Silva NIO, de Oliveira JS, Kroon EG, Trindade GS, Drumond BP. Here, There, and Everywhere: The Wide Host Range and Geographic Distribution of Zoonotic Orthopoxviruses. Viruses. 2020 Dec 30;13(1):43. PubMed: https://pubmed.gov/33396609. Full text: https://doi.org/10.3390/v13010043

The authors review the global host ranges and current epidemiological understanding of zoonotic orthopoxviruses while focusing on orthopoxviruses with epidemic potential, including monkeypox, cowpox, and vaccinia viruses.


5 November 2020

Alakunle E, Moens U, Nchinda G, Okeke MI. Monkeypox Virus in Nigeria: Infection Biology, Epidemiology, and Evolution. Viruses. 2020 Nov 5;12(11):1257. PubMed: https://pubmed.gov/33167496. Full text: https://doi.org/10.3390/v12111257

A review about the 2020 state of knowledge about “the infection biology, epidemiology, and evolution of MPXV in Nigeria and worldwide, especially with regard to the human, cellular, and viral factors that modulate the virus transmission dynamics, infection, and its maintenance in nature.”


16 October 2019

Beer EM, Rao VB. A systematic review of the epidemiology of human monkeypox outbreaks and implications for outbreak strategy. PLoS Negl Trop Dis. 2019 Oct 16;13(10):e0007791. PubMed: https://pubmed.gov/31618206. Full text: https://doi.org/10.1371/journal.pntd.0007791. eCollection 2019 Oct

Final sentence: “While monkeypox virus has not established and propagated itself in the human population since the cessation of smallpox vaccination, the risks to populations in endemic areas are evident. Significant improvements in the quality and quantity of outbreak data collection are urgently needed to improve the monkeypox research portfolio to inform appropriate case management and public health response.” 86 references.


10 July 2019

Yinka-Ogunleye A, Aruna O, Dalhat M, et al. Outbreak of human monkeypox in Nigeria in 2017-18: a clinical and epidemiological report. Lancet Infect Dis. 2019 Aug;19(8):872-879. PubMed: https://pubmed.gov/31285143. Full text: https://doi.org/10.1016/S1473-3099(19)30294-4

After 39 years without detection of human disease in Nigeria, an outbreak involving 122 confirmed or probable cases was identified during 2017–2018, including seven deaths (case fatality rate 6%). “People infected with monkeypox virus were aged between 2 days and 50 years (median 29 years [IQR 14]), and 84 (69%) were male. All 122 patients had vesiculopustular rash, and fever, pruritus, headache, and lymphadenopathy were also common. The rash affected all parts of the body, with the face being most affected.”


15 April 2019

Makhani L, Khatib A, Corbeil A, et al. 2018 in review: five hot topics in tropical medicine. Trop Dis Travel Med Vaccines. 2019 Apr 15;5:5. PubMed: https://pubmed.gov/31016025. Full text: https://doi.org/10.1186/s40794-019-0082-z

Prescient: “Moreover, exportation of disease serves to remind clinicians that monkeypox remains part of the differential diagnosis in individuals presenting with widespread vesiculopustular rash, fever, and lymphadenopathy, particularly with a history of travel to West or Central Africa, understanding that with the globalization of the exotic animal trade, local transmissions could essentially occur anywhere.”


26 October 2018

Kabuga AI, El Zowalaty ME. A review of the monkeypox virus and a recent outbreak of skin rash disease in Nigeria. J Med Virol. 2019 Apr;91(4):533-540. PubMed: https://pubmed.gov/30357851. Full text: https://doi.org/10.1002/jmv.25348

This outbreak in Nigeria consisted of 262 suspected, 115 confirmed cases, and 7 mortalities across 26 states and the Federal Capital Territory (FCT), Abuja.


4 September 2018

Sklenovská N, Van Ranst M. Emergence of Monkeypox as the Most Important Orthopoxvirus Infection in Humans. Front Public Health. 2018 Sep 4;6:241. PubMed: https://pubmed.gov/30234087. Full text: https://doi.org/10.3389/fpubh.2018.00241

The objective of this review (118 references) was to trace all reported human monkeypox outbreaks and relevant epidemiological information. In 2018, the authors warned that the frequency and geographical spread of human monkeypox cases had increased in recent years.


20 June 2012

Reynolds MG, Carroll DS, Karem KL. Factors affecting the likelihood of monkeypox’s emergence and spread in the post-smallpox era. Curr Opin Virol. 2012 Jun;2(3):335-43. PubMed: https://pubmed.gov/22709519. Full text: https://doi.org/10.1016/j.coviro.2012.02.004

Monkeypox virus is a less efficient human pathogen than the agent of smallpox, but absent smallpox and the population-wide immunity engendered during eradication efforts, could monkeypox now gain a foothold in human communities?


1 March 2007

Bernard SM, Anderson SA. Qualitative assessment of risk for monkeypox associated with domestic trade in certain animal species, United States. Emerg Infect Dis. 2006 Dec;12(12):1827-33. PubMed: https://pubmed.gov/17326932. Full text: https://doi.org/10.3201/eid1212.060454

An assessment of the 2003 monkeypox outbreak in the US. (As a reminder, the virus was likely introduced through a shipment of imported African rodents, which were kept with other mammals, including prairie dogs, in a pet distribution facility in the Midwest.) The authors conclude that the probability of further human infection is low and that the risk would be further mitigated by rodent import restrictions.


9 November 2005

Kile JC, Fleischauer AT, Beard B, et al. Transmission of monkeypox among persons exposed to infected prairie dogs in Indiana in 2003. Arch Pediatr Adolesc Med. 2005 Nov;159(11):1022-5. PubMed: https://pubmed.gov/16275790. Full text: https://doi.org/10.1001/archpedi.159.11.1022

A cluster of human monkeypox cases associated with exposure to ill prairie dogs in a home child care. Nine (13%) of 70 persons exposed to the prairie dogs reported signs and symptoms of monkeypox.


22 January 2004

Reed KD, Melski JW, Graham MB, et al. The detection of monkeypox in humans in the Western Hemisphere. N Engl J Med. 2004 Jan 22;350(4):342-50. PubMed: https://pubmed.gov/14736926. Full text: https://doi.org/10.1056/NEJMoa032299

Description of the 11 initial cases of the 2003 outbreak in the United States, five males and six females ranging in age from 3 to 43 years.


18 May 1999

Heymann DL, Szczeniowski M, Esteves K. Re-emergence of monkeypox in Africa: a review of the past six years. Br Med Bull. 1998;54(3):693-702. PubMed: https://pubmed.gov/10326294. Full text: https://doi.org/10.1093/oxfordjournals.bmb.a011720

“In August 1996, an unusually large outbreak of human monkeypox was reported, and cases continued through 1997 with peak incidence in August 1996, March 1997 and August 1997. Preliminary results from the field investigations in 1997 suggest a new epidemiological pattern where a majority of secondary cases result from person-to-person transmission, and a clinically milder diseases.”