Human-to-human transmission

Human-to-human transmission (HHT) is a particularly problematic epidemiologic vector,[1][2][3][4][5][6][7][8] especially in case the disease is borne by individuals known as superspreaders. In these cases, the basic reproduction number of the virus, which is the average number of additional people that a single case will infect without any preventative measures, can be as high as 3.9.[9][10] Interhuman transmission is a synonym for HHT.[11]

The World Health Organization designation of a pandemic hinges on the demonstrable fact that there is sustained HHT in two regions of the world.[12]

Synopsis

Relevant pathogens may be viruses, bacteria, or fungi, and they may be spread through breathing, talking, coughing, sneezing, spraying of liquids, toilet flushing or any activities which generate aerosol particles or droplets or generate fomites, such as raising of dust.[13][14]

A 2007 study showed that influenza virus was still active on stainless steel 24 hours after contamination. Though on hands it survives only for five minutes, the constant contact with steel almost certainly transmits infection.[15] Transfer efficiency depends not only on surface, but also on pathogen type. For example, avian influenza survives on both porous and non-porous materials for 144 hours.[13]

The pathogens may also be transmitted by poor use of cutlery or improper sanitation of dishes or bedlinen. Particularly problematic are toilet practices, which lead to the fecal-oral route. STDs are by definition spread through this vector.

List of HHT diseases

Examples of some HHT diseases are listed below.

Controlled

• measles: vaccine available
• mumps: vaccine available
• chicken pox: vaccine available
• small pox[16]
• bubonic plague: slim non-nil risk[17]
• pneumonic plague: 1910-11 Manchurian plague[18]
• tuberculosis
• Norovirus[19][20]
• monkeypox[21]
• SARS-CoV-1
• MERS
• Avian flu
• Sexually transmitted infections (STIs) or sexually transmitted diseases (STDs):
  • Syphilis, aka French pox[16]

Uncontrolled

• SARS-CoV-2

References

1. Chowell, Gerardo; Blumberg, Seth; Simonsen, Lone; Miller, Mark A.; Viboud, Cécile (2014). "Synthesizing data and models for the spread of MERS-CoV, 2013: Key role of index cases and hospital transmission". Epidemics. 9: 40–51. doi:10.1016/j.epidem.2014.09.011. PMC 4258236. PMID 25480133.
2. Virlogeux, Victor; Feng, Luzhao; Tsang, Tim K.; Jiang, Hui; Fang, Vicky J.; Qin, Ying; Wu, Peng; Wang, Xiling; Zheng, Jiandong; Lau, Eric H. Y.; Peng, Zhibin; Yang, Juan; Cowling, Benjamin J.; Yu, Hongjie (2018). "Evaluation of animal-to-human and human-to-human transmission of influenza A (H7N9) virus in China, 2013–15". Scientific Reports. 8 (1): 552. Bibcode:2018NatSR...8..552V. doi:10.1038/s41598-017-17335-9. PMC 5765021. PMID 29323268.
3. Majumder, Maimuna S.; Brownstein, John S.; Finkelstein, Stan N.; Larson, Richard C.; Bourouiba, Lydia (2017). "Nosocomial amplification of MERS-coronavirus in South Korea, 2015". Transactions of the Royal Society of Tropical Medicine and Hygiene. 111 (6): 261–269. doi:10.1093/trstmh/trx046. PMC 6257029. PMID 29044371.
4. De Graaf, Miranda; Beck, Relja; Caccio, Simone M.; Duim, Birgitta; Fraaij, Pieter LA; Le Guyader, Françoise S.; Lecuit, Marc; Le Pendu, Jacques; De Wit, Emmie; Schultsz, Constance (2017). "Sustained fecal-oral human-to-human transmission following a zoonotic event". Current Opinion in Virology. 22: 1–6. doi:10.1016/j.coviro.2016.11.001. PMC 7102779. PMID 27888698.
5. Geoghegan, Jemma L.; Senior, Alistair M.; Di Giallonardo, Francesca; Holmes, Edward C. (2016). "Virological factors that increase the transmissibility of emerging human viruses". Proceedings of the National Academy of Sciences. 113 (15): 4170–4175. Bibcode:2016PNAS..113.4170G. doi:10.1073/pnas.1521582113. PMC 4839412. PMID 27001840.
6. Kucharski, Adam; Mills, Harriet; Pinsent, Amy; Fraser, Christophe; Van Kerkhove, Maria; Donnelly, Christl A.; Riley, Steven (2014). "Distinguishing Between Reservoir Exposure and Human-to-Human Transmission for Emerging Pathogens Using Case Onset Data". PLOS Currents. 6. doi:10.1371/currents.outbreaks.e1473d9bfc99d080ca242139a06c455f. PMC 3946006. PMID 24619563.
7. Herfst, Sander; Böhringer, Michael; Karo, Basel; Lawrence, Philip; Lewis, Nicola S.; Mina, Michael J.; Russell, Charles J.; Steel, John; De Swart, Rik L.; Menge, Christian (2017). "Drivers of airborne human-to-human pathogen transmission". Current Opinion in Virology. 22: 22–29. doi:10.1016/j.coviro.2016.11.006. PMC 7102691. PMID 27918958.
8. Riou, Julien; Althaus, Christian L. (2020). "Pattern of early human-to-human transmission of Wuhan 2019 novel coronavirus (2019-nCoV), December 2019 to January 2020". Eurosurveillance. 25 (4). doi:10.2807/1560-7917.ES.2020.25.4.2000058. PMC 7001239. PMID 32019669.
9. Li Q, Guan X, Wu P, Wang X, Zhou L, Tong Y, et al. (January 2020). "Early Transmission Dynamics in Wuhan, China, of Novel Coronavirus-Infected Pneumonia". The New England Journal of Medicine. 382 (13): 1199–1207. doi:10.1056/NEJMoa2001316. PMC 7121484. PMID 31995857.
10. Riou J, Althaus CL (January 2020). "Pattern of early human-to-human transmission of Wuhan 2019 novel coronavirus (2019-nCoV), December 2019 to January 2020". Euro Surveillance. 25 (4). doi:10.2807/1560-7917.ES.2020.25.4.2000058. PMC 7001239. PMID 32019669.
11. Meyer, A.; Esposito, J. J.; Gras, F.; Kolakowski, T.; Fatras, M.; Muller, G. (1991). "First appearance of monkey pox in human beings in Gabon". Médecine Tropicale : Revue du Corps de Santé Colonial. 51 (1): 53–7. PMID 1649373.
12. Friscolanti, Michael (4 June 2009). "Canada's Pandemic Influenza Plan". Canadian Encyclopedia.
13. Cook 2013, p. 208.
14. Abad, F. X.; R. M. Pintó; A. Bosch (October 1994). "Survival of enteric viruses on environmental fomites". Applied and Environmental Microbiology. 60 (10): 3704–10. doi:10.1128/AEM.60.10.3704-3710.1994. PMC 201876. PMID 7986043.
15. Larson & Liverman 2011, p. 41.
16. Welford, Mark R.; Bossak, Brian H.; Carter, Dee A. (22 December 2009). "Validation of Inverse Seasonal Peak Mortality in Medieval Plagues, Including the Black Death, in Comparison to Modern Yersinia pestis-Variant Diseases". PLOS ONE. 4 (12): e8401. Bibcode:2009PLoSO...4.8401W. doi:10.1371/journal.pone.0008401. PMC 2791870. PMID 20027294.
17. Kool, Jacob L. (2005). "Risk of Person‐to‐Person Transmission of Pneumonic Plague". Clinical Infectious Diseases. 40 (8): 1166–1172. doi:10.1086/428617. PMID 15791518.
18. Wilson, Mark (24 March 2020). "The untold origin story of the N95 mask". Fast Company.
19. Kumar Nag, Pranab (2018). Office Buildings: Health, Safety and Environment. Springer. p. 85. ISBN 9789811325779.
20. Robilotti, Elizabeth; Deresinski, Stan; Pinsky, Benjamin A. (2015). "Norovirus". Clinical Microbiology Reviews. 28 (1): 134–164. doi:10.1128/CMR.00075-14. PMC 4284304. PMID 25567225.
21. Learned, L. A.; Reynolds, M. G.; Wassa, D. W.; Li, Y.; Olson, V. A.; Karem, K.; Stempora, L. L.; Braden, Z. H.; Kline, R.; Likos, A.; Libama, F.; Moudzeo, H.; Bolanda, J. D.; Tarangonia, P.; Boumandoki, P.; Formenty, P.; Harvey, J. M.; Damon, I. K. (2005). "Extended interhuman transmission of monkeypox in a hospital community in the Republic of the Congo, 2003". The American Journal of Tropical Medicine and Hygiene. 73 (2): 428–34. doi:10.4269/ajtmh.2005.73.428. PMID 16103616.

Sources

• Cook, Nigel (2013). "10.1 Introduction; the role of fomites in the virus transmission". Viruses in Food and Water: Risks, Surveillance and Control. Cambridge: Woodhead Publishing. pp. 205–215. ISBN 978-0-85709-887-0.
• Larson, Elaine L.; Liverman, Catharyn T. (2011). "Understanding the Risk to Healthcare Personnel: Fomite Persistence". Preventing Transmission of Pandemic Influenza and Other Viral Respiratory Diseases: Personal Protective Equipment for Healthcare Personnel: Update 2010. Washington: National Academies Press. p. 41. ISBN 978-0-309-16254-8.