Monkeypox, the silently emerging threat


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Monkeypox is not a rare disease anymore. Appropriate and effective interventions and active surveillance activities are urgently needed to make sure that monkeypox won’t become the new smallpox.

 

Monkeypox (caused by Monkeypox virus, genus Orthopoxvirus) has long been thought to be a rare disease occurring in humans only sporadically1. But after its “cousin” variola (causing smallpox) was eradicated in 19802 and the vaccination was stopped3, it left more people every year vulnerable to all orthopoxvirus infections. This, together with higher exposure to possibly infected animals because of anthropogenic and demographic changes in the last decades, caused a 20-fold increase in monkeypox incidence4. Today, monkeypox is endemic in the Democratic Republic of Congo (DRC) and occurs also in other countries of western and central Africa5. It already left the African continent once when rodents shipped from Ghana to the USA in 2003 caused an outbreak counting 47 cases6-8.

It is estimated that 75% of the (re-)emerging pathogens are zoonotic9 and a striking number of newly described zoonoses is linked to an expanding global population and accelerated global changes10. Drastic wildlife reduction, global climate changes, changes in agricultural practices, wildlife trade, traveling and migration of people are hot topics of the last decades which are closely linked to the (re-)emergence or introduction of a new pathogen into a population211,13. Recently we have seen such pathogens (e.g. Ebola and Zika) to emerge and cause an epidemic. So we are aware of the dangers that zoonotic pathogens constitute and we know that they will emerge and possibly cause an epidemic or pandemic more frequently in the future. Yet, we still rather spend much more money for response and control of outbreaks than less money for research and surveillance before it emerges so that we could be more prepared and possibly prevent it. Before the Ebola outbreak in 2014, there was no treatment or vaccine even though we knew about the virus since 1976. This Ebola outbreak cost more than $3,6 billion (not mentioning the lives and GDP loss of the three affected countries)14 while it is estimated that it would cost only about $3,4 billion to identify 99% of high-consequence viruses in wildlife hosts that are most likely to carry the next pandemic15.

Monkeypox outbreak reports are often incomplete because the data are nowadays acquired through a passive surveillance program. It has been shown that passive surveillance systems often miss most cases, leading to an underestimation of the burden of MPXV infections in humans4, 16. In the DRC, this is largely due to years of civil war throughout the country which has made surveillance activities, but also research on the ecology, epidemiology, natural history and pathogenesis of the infection very difficult. It means that most recent data on MPX cases are probably significantly underreported leading to underestimating the magnitude of the problem.

Monkeypox pic

Monkeypox virus currently belongs to the “biosafety level 3” category, the “high threat” biodefence category in the EU17 and is on the list of select agents in the USA18. In any of the following cases, the treat would further increase virulence increase (both naturally19,20 or genetic engineering21), virus spill into more widely distributed taxa22 or introduction in other continents4. In fact, we are probably allowing the virus to increase its virulence by not controlling its transmission, partially because of not knowing about all monkeypox cases. Moreover, an unintentional import of a disease to a new continent is nowadays fairly easy due to air transportation. And yet, there is too little research being done about the topic and not all generated data is published for various reasons. The latter is an issue limiting scientific progress in any research area but is even more pronounced in the field of neglected tropical disease where much is unknown.

Monkeypox is not a rare disease anymore. Its incidence in the DRC increased 20-fold compared to 1980s4 and some sources suggest changes in transmission rate23 and mortality rate24. Appropriate and effective interventions and active surveillance activities are urgently needed to make sure that monkeypox won’t become the new smallpox22.

 

References

  1. The current status of human monkeypox: Memorandum from a WHO Meeting. Bull World Health Organ. 1984;62(5):703-13.
  2. Breman JG, Arita I. The confirmation and maintenance of smallpox eradication. N Engl J Med. 1980;303(22):1263-73.
  3. Jezek Z, Khodakevich LN, Wickett JF. Smallpox and its post-eradication surveillance. Bull World Health Organ. 1987;65(4):425-34.
  4. Rimoin AW, Mulembakani PM, Johnston SC, Lloyd Smith JO, Kisalu NK, Kinkela TL, et al. Major increase in human monkeypox incidence 30 years after smallpox vaccination campaigns cease in the Democratic Republic of Congo. Proc Natl Acad Sci USA 2010;107(37):16262-7.
  5. Meyer H, Perrichot M, Stemmler M, Emmerich P, Schmitz H, Varaine F, et al. Outbreaks of disease suspected of being due to human monkeypox virus infection in the Democratic Republic of Congo in 2001. J Clin Microbiol. 2002;40(8):2919-21.
  6. CDC. 2003 U.S. Outbreak. 2015 [accessed 23/01/2017]. Available from: https://www.cdc.gov/poxvirus/monkeypox/outbreak.html.
  7. Reed KD, Melski JW, Graham MB, Regnery RL, Sotir MJ, Wegner MV, et al. The detection of monkeypox in humans in the Western Hemisphere. N Engl J Med. 2004;350(4):342-50.
  8. Multistate outbreak of monkeypox—Illinois, Indiana, and Wisconsin, 2003. Centers for Disease Control and Prevention, 2003 Contract No.: 23.
  9. Taylor LH, Latham SM, Woolhouse ME. Risk factors for human disease emergence. Philos Trans R Soc Lond B Biol Sci. 2001;356(1411):983-9.
  10. Karesh WB, Dobson A, Lloyd-Smith JO, Lubroth J, Dixon MA, Bennett M, et al. Ecology of zoonoses: natural and unnatural histories. Lancet. 2012;380(9857):1936-45.
  11. Chomel BB, Belotto A, Meslin Fç X. Wildlife, Exotic Pets, and Emerging Zoonoses. Emerg Infect Dis. 2007;13(1):6-11.
  12. Barnett ED, Walker PF. Role of immigrants and migrants in emerging infectious diseases. Med Clin North Am. 2008;92(6):1447-58.
  13. Rohr JR, Dobson AP, Johnson PTJ, Kilpatrick AM, Paull SH, Raffel TR, et al. Frontiers in climate change-disease research. Trends Ecol Evol. 2011;26(6):270-7.
  14. CDC. Cost of the Ebola Epidemic 2016 [accessed 7/8/2017]. Available from: https://www.cdc.gov/vhf/ebola/outbreaks/2014-west-africa/cost-of-ebola.html.
  15. TheGlobalViromeProject. Fighting outbreaks before they happen makes good sense. Available from: http://www.globalviromeproject.org/moreau.
  16. Mwamba DK, Kebela BI, Shongo RL, Pukuta E, Kayembe NJM. Profil épidemiologique du monkeypox en RDC, 2010-2014. Ann Afr Med. 2014;8(1):1855-60.
  17. Tian D, Zheng T. Comparison and Analysis of Biological Agent Category Lists Based On Biosafety and Biodefense. PLoS One. 2014;9(6).
  18. FSAP. Select Agents Regulations, 42 C.F.R. Part 73. 2017.
  19. Shchelkunov SN, Marennikova SS, Moyer RW. Classification of poxviruses and brief characterization of the genus. Orthopovxiruses pathogenic for humans. USA: Springer; 2005.
  20. Blumberg S, Lloyd-Smith JO. Inference of R0 and Transmission Heterogeneity from the Size Distribution of Stuttering Chains. PLoS Comput Biol. 2013;9(5).
  21. Jackson RJ, Ramsay AJ, Christensen CD, Beaton S, Hall DF, Ramshaw IA. Expression of mouse interleukin-4 by a recombinant ectromelia virus suppresses cytolytic lymphocyte responses and overcomes genetic resistance to mousepox. J Virol. 2001;75(3):1205-10.
  22. 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;2(3):335-43.
  23. Learned LA, Reynolds MG, Wassa DW, Li Y, Olson VA, Karem K, et al. Extended interhuman transmission of monkeypox in a hospital community in the Republic of the Congo, 2003. Am J Trop Med Hyg. 2005;73(2):428-34.
  24. ElPais. La viruela de los monos, ese nuevo desafío 2017 [28/7/2017]. Available from: La viruela de los monos, ese nuevo desafío.

 

 

Sklenovska_pic Nikola Sklenovská is a young global health professional with a master in Biomedical Sciences. Nikola’s main interests are emerging infectious diseases. With her work, she wants to have a positive impact in the World while discovering new perspectives and ideas.

 

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