Timeline of contact tracing

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This is a timeline of contact tracing, attempting to describe significant events in the history of this tool.

Sample questions

The following are some interesting questions that can be answered by reading this timeline:

  • What are some types of infections having been traced along the history of contact tracing?
  • What are some early vestiges of practices preluding the development of contact tracing?
    • Sort the full timeline by "Event type" and look for the group of rows with value "Early development".
    • You will see some early attempts to trace disease outbreaks.
  • What are some illustrative events representing the further development of the field of contact tracing?
    • Sort the full timeline by "Event type" and look for the group of rows with value "Field development".
    • You will see some events on research, some analyzing contact tracing effectiveness, and others introducing new models, like SIR, as well as other tools of analysis.
  • What are some examples of adoption of contact tracing throughout history?
    • Sort the full timeline by "Event type" and look for the group of rows with value "Adoption".
    • You will see a number of events describing adoption of contact tracing, often to trace venereal diseases.
    • You will mostly see early adoption by some contries in the mid-20th century.
  • What are some notable cases of use of contact tracing during infection outbreaks?
    • Sort the full timeline by "Event type" and look for the group of rows with value "Performance".
    • You will see some successful cases of adoption of contact tracing.
  • What are some notable technologies being introduced as tools for contact tracing?
    • Sort the full timeline by "Event type" and look for the group of rows with value "Technology introduction".
    • You will mostly see events describing the introduction of digital contact tracing, smartphones, and Bluetooth.
  • What are some illustrative events describing the publication of books on contact tracing?
    • Sort the full timeline by "Event type" and look for the group of rows with value "Literature".
  • Other events are described under the following types: "Background", "Criticism", "Notable case", "Recommendation", and "Training".

Big picture

Time period Development summary More details
Before 19th century Early vestiges Vestiges of practices that would later evolve to contact tracing can be found as early as in the 16th century, during the Renaissance.[1]
19th century Modern science development Bacteriology emerges as a new science, and a vast workforce of sanitary inspectors is assembled in the United States and especially in the United Kingdom, which is acknowledged as a leader in the creation of an infectious disease surveillance system of notification, isolation, disinfection, and case finding. [2] John Snow is considered by some to be the first having used contact tracing.
20th century Modern contact tracing development Modern contact tracing is developed in the United States, first in response to syphilis, and later expanded to include other sexually transmitted infections.[3] Since then, contact tracing, also known as partner notification, is regarded as a key element in the control of sexually transmitted infections and starts being implemented in many parts of the world.[4][5] Since the 1980s, modellers start developing a consistent theory for contact tracing, with the aim to find effective and efficient implementations, and to assess the effects of contact tracing on the spread of an infectious disease.[6]
21st century Digital contact tracing emergence The concept of digital contact tracing originates. In 2014 Bluetooth technology for digital contact tracing is first validated, and smartphones become the main device for contact tracing in this century.
2020 onwards COVID-19 pandemic The COVID pandemic presents a new avenue for surveillance capitalism through electronic contract tracing. The Centers for Disease Control Prevention (CDC)[7] develops guidelines for digital contact tracing processes and mobile applications. Apple and Google partner to develop a Privacy-Preserving Contact Tracing[8] statement to provide guidance for individual developers, public health departments, and others who may be utilizing their technologies to create apps and processes for tracing the spread and existence of COVID-19 in communities and regions.

Numerical and visual data

Google Scholar

The following table summarizes per-year mentions on Google Scholar as of May 22, 2021.

Year contact tracing contact tracing tuberculosis contact tracing ebola contact tracing covid 19 (since 2019) digital contact tracing contact tracing privacy
1980 4,320 95 8 457 595
1985 5,440 133 13 671 584
1990 7,940 230 12 1,310 1,300
1995 13,400 396 13 1,830 2,260
2000 26,200 814 58 3,590 8,320
2002 32,600 1,010 83 4,190 9,200
2004 40,900 1,250 136 6,180 12,500
2006 54,500 1,320 115 8,130 18,400
2008 65,600 1,720 190 9,700 27,500
2010 75,600 1,950 174 12,000 40,100
2012 88,700 2,370 153 15,200 54,300
2014 88,700 2,510 628 18,500 61,100
2016 80,000 2,690 1,190 22,100 59,500
2017 74,400 2,770 964 23,500 56,600
2018 67,100 2,920 961 26,000 54,100
2019 56,200 2,880 1,060 2,130 26,700 45,300
2020 52,400 4,980 4,500 25,500 28,800 40,600
Contact tracing tb.png

Google Trends

The comparative chart below shows Google Trends data for Contact tracing (Search term) and tracing app (Search term), from April 2016 to April 2021, when the screenshot was taken. Interest is also ranked by country and displayed on world map. See spike towards 2020, as a result of the Covid-19 pandemic.[9]

Contact tracing and tracing app gt.png

Google Ngram Viewer

The chart below shows Google Ngram Viewer data for Contact tracing, from 1900 to 2019.[10]

Contact tracing ngram.png

Wikipedia Views

The chart below shows pageviews of the English Wikipedia article Contact tracing on desktop, mobile-web, desktop-spider, mobile-web-spider and mobile app, from July 2015; to December 2020.[11]

Contact tracing wv.jpeg

Full timeline

Year Event type Infection Details Location
1530 Early development Syphilis A poem by the physician Girolamo Fracastoro indicates the idea behind contact tracing, during a syphilis epidemic.[1] Italy
1530s Early development Syphilis Italian physician Bernardino Tomitano follows syphilis’s continued spread into eastern Europe, pinning it to Venetian commerce.[1] Italy, Eastern Europe
1576 Early development Bubonic plague While treating patients in northern Italy during a bubonic plague outbreak, physician Andrea Gratiolo uses contact tracing not to trace the spread of plague as such, but to disprove that it derives from a woman who is rumoured to have carried it from where she lived.[1] Italy
1760 Early development Smallpox The earliest account of mathematical modelling of spread of disease is carried out by Daniel Bernoulli, who manages to model the spread of smallpox, which is prevalent at the time.[12] Switzerland
1840s Early development Yellow fever Physicians in France fighting yellow fever focus on finding the first case, what today we call patient zero. In the late century, they would begin paying greater attention to connections between households, and people inside and outside of them.[1] France
1854–1855 Early development Cholera During the 1854 Broad Street cholera outbreak in London, Dr. John Snow collects data about the individual cases, especially their location in Soho, using nascent methods of spatial analysis and contact tracing to conclude that contaminated water is the disease vector, and successfully has the source shut off.[13] The map accompanying his 1855 report shows individual cases, stacked at each house location, clearly showing a concentration around the Broad Street Pump as well as gaps in locations that had other water sources.[14] The map would later be hailed as revolutionary, being considered the most effective tool for communicating the spatial patterns of the disease.[15] This is considered by some to be the first time contact tracing is used.[16] United Kingdom
1890 Adoption Statutory powers in Glasgow (later throughout Scotland), are granted for the maintenance of a “reception house” for people who have been in contact with infectious diseases and were living in overcrowded dwellings.[17] United Kingdom (Scotland)
1893 Literature Albert Taylor publishes the first edition of his Sanitary Inspector’s Handbook, which states that the sanitary inspector should visit and inspect the home of each infected person, arrange for the patient’s removal, search for possible disease sources, schedule disinfection procedures, and inquire about contacts.[17]
1900–1907 Notable case Typhoid fever Contact tracing is used to identify Mary Mallon (later called Typhoid Mary), an asymptomatic carrier of typhoid working as a cook in the New York area. She is found by researcher George Soper to be the link to isolated outbreaks of the disease in rich households, an unusual occurrence as at this time it is known that typhoid is generally passed through unclean environments.[18][19] United States
1910 Concept development Revitalized during the Covid-19 pandemic, the term "contact tracing" is added to the Oxford English Dictionary in their July 2020 update. It describes the process of identifying individuals who may have come into contact with someone infected with a disease. "Contact tracer" is also added as the term to describe someone who is responsible for identifying those individuals.[20]
1923–1937 Adoption Protective public health services, such as contact tracing, are codified into Turkish law in this period.[21] Turkey
1927 Field development The SIR model (Susceptible, Infectious, or Recovered) is first published. This mathematical model is the most basic approach to find a number of ways to anticipate what will happen in a pandemic.[22]
1927 Field development The Kermack–McKendrick epidemic model is introduced, having a major influence on the development of mathematical models for disease spread. In the 21st century,it is still relevant in many epidemic situations.[23][24]
1920s Adoption Contact tracing becomes increasingly used as infectious disease control in the United States, more than social distancing.[25] United States
1928 Notable case Syphilis The Soviet–German Syphilis Expedition takes place as a joint Soviet and German expedition comprising eight medical researchers from each country with purpose was to investigate endemic syphilis in the Buryat-Mongolian Autonomous Republic to determine the efficacy of the anti-syphilis drug Salvarsan. The expedition concludes, contrary to expectations, that although affected by poor sanitation and lifestyle, the spread of syphilis in the area is caused primarily by sexual activity.[26][27] Russia
1930s Adoption Sexually transmitted infection The British Goverment adopts contact tracing as one of the primary weapons to contain the incidence of sexually transmitted diseases.[28] United Kingdom
1937 Literature Syphilis U.S. Surgeon General Thomas Parran publishes Shadow on the Land, a book about syphilis control , in which he describes contact tracing in detail.[29] United States
1941 Adoption Sexually transmitted infection In an effort to combat venereal diseases, contact tracers are officially introduced in New Zealand after training public health nurses.[30] New Zealand
1947 Adoption Sexually transmitted infection Mandatory contact tracing is introduced in Denmark as a measure to combact venereal diseases.[31] Denmark
1948 Background The World Health Organization (WHO) is founded as a specialized agency of the United Nations with the primary responsibility for international health matters and public health.[32]
1962 Adoption Smallpox Contact tracing is conducted in over 1,400 individuals during the Bradford smallpox outbreak.[33] United Kingdom (England)
1962 Training Sexually transmitted infection Following the increasing acknowledgment of same-sex contacts by men attending venereal disease clinics in England and North America, training courses start instructing contact tracers on how to identify homosexuals, in a positivist nineteenth-century sexological project of defining and identifying "sexual deviants". Training also includes explaining that "certain known occupations may suggest deviant sexual activity".[34] North America, United Kingdom
1960s Adoption In the United Kingdom, the work of contact tracing falls to staff of what would be later called the environmental health department. In this decade, contact tracers are known as health inspectors and, in an emergency, they would arrive to the place under the jurisdiction of the local medical officer of health.[35] United Kingdom
1978 Concept development Yorke et al. introduce the concept of a core group, which postulates that epidemics or endemics of sexually transmitted disease are maintained by a small group of sexually active individuals who persistently infect other healthy people. Those core group members, due to their active sexual life, inevitably behave like the central point of a star connecting to a large number of others in a network.[36]
1978 Technology introduction The Global Positioning System (GPS) is first introduced.[37] United States
1979 Performance Smallpox Smallpox is officially declared eradicated worldwide, largely as a result of global and local contact tracing efforts.[38][39][40][38] Worldwide
1984 Adoption HIV Auerbach et al. initiate a contact investigation of 19 patients in California to assess the role of sexual relationships in AIDS transmission. They eventually link 40 patients across ten cities in the United States in a network graph, supporting the long held hypothesis that AIDS is transmitted via pathogens.[36]
1984 Field development Gonorrhoea A study by Hethcote and Yorke concerning interventions for gonorrhoea becomes one of the first papers addressing models for contact tracing. The researchers suggest that the impact of contact tracing is caused by a reduction in the effective transmissibility of the infection.[6]
1985 Adoption HIV American epidemiologist Michael Osterholm, at the University of Minnesota, starts the first contact tracing program for HIV.[41] United States
1985 Field development Alden S. Klovdahl formally establishes the connection between contact tracing and social network analysis, demonstrating how the latter could be applied to examine two causal criteria of transmission: exposure and temporality.[36]
1986 Adoption HIV A contact-tracing detection system is set up in Cuba, allowing the reconstruction and analysis of the sexual network underlying the epidemic of HIV/AIDS.[42] Cuba
1987 Literature Yellow fever American historian William Coleman’s publishes Yellow Fever in the North, which associates “case tracing” with the origins of epidemiology in the mid-19th century.[1]
1987 Adoption HIV Contact tracing becomes a near mandatory process to track the spread of HIV, with or without the patient’s consent. If people infected are unwilling to notify their partners ... physicians or health department personnel wouldbe required to use confidential procedures to assure that the partners are notified.[43] United States
1994 Concept development Klovdahl et al. prove the concept of incorporating social network analysis into disease investigation.[36]
1996 Concept development Sexually transmited infection Thomas and Tucker describe core group and bridges as key individuals in social network analysis during an outbreak of sexually transmited disease.[36]
2002-2004 Performance Severe acute respiratory syndrome The OECD reports on a successful use of contact tracing during the 2002–2004 SARS outbreak.[44]
2003 Field development Hyman, Li, and Stanley propose that contact tracing is based on the identification of infected persons by their infected contacts. "In that, the “superinfection” is taken verbally, and infecteds are removed from the infectious compartment with a term that resembles the incidence term (product of discovered infecteds and prevalence)."[6]
2005 Field development Hsieh et al. compare predictions of different ways of modelling contacr tracing - linear, mass action, and a saturation function - with data. The authors conclude that a mass action term for contact tracing is inferior to a linear term or a saturation function.[6]
2007 Technology introduction The concept of digital contact tracing likely originates in this year.[45][46]
2007 Concept development Romanian-born Hungarian-American physicist Albert-László Barabási coins and popularizes the term network medicine. Barabási states that biological systems, similarly to social and technological systems, contain many components that are connected in complicated relationships but are organized by simple principles.[47] Epidemic models and concepts, such as spreading and contact tracing, would be adapted to be used in network analysis.[48]
2007 Field development K.T. Eames compares recursive and one-step tracing. He also analyzes “targeted contact tracing”, that is, contact tracing focusing on a risk group. Recursive and targeted contact tracing are found to be particularly effective.[6]
2009 Performance Influenza Contact tracing is successfuly conducted in Taiwan during the 2009 swine flu pandemic[49] Along with prophylactic treatment, enhanced contact tracing manage to stop local transmission of the virus and no other domestic cases would be found.[50] Taiwan
2010 Field development Study by House and Keeling finds that contact tracing is more effective in clustered than in homogeneous populations.[6]
2012 Field development Chlamydia Clarke, White, and Turner apply pair approximation to predict the impact of contact tracing on chlamydia prevalence.[6]
2012 Performance Middle East respiratory syndrome–related coronavirus Contact tracing is successfully used in the United Arab Emirates during the Middle East respiratory syndrome outbreak. It is early initiated, along with case investigation, after the first incident report.[44] United Arab Emirates
2014 Technology introduction Bluetooth technology for digital contact tracing is first validated when it proves to be effective in the first empirical investigation using Bluetooth data.[51][52][53]
2014 Performance Ebola Contact tracing is conducted as a successful program during the West African Ebola virus epidemic, being part of a multi-pronged public health response that would prove to be effective in containing the spread of the virus after its initial spread. Global health agencies successfully eliminate the outbreak in Sierra Leone, the worst affected country, by monitoring contacts of infected individuals and preemptively managing those who have come into contact with the infected.[38][54] Sierra Leone, West Africa
2018 Technology introduction A patent application by Facebook discusses a Bluetooth proximity-based trust method.[55]
2019 Technology introduction Ebola A smartphone app is successfully employed for contact tracing in hotspots of ebola in the Democratic Republic of the Congo.[56] Democratic Republic of the Congo
2020 Technology introduction COVID-19 Apple and Google, who account for most of the world's mobile operating systems at the time, announce COVID-19 apps for iOS and Android.[57]
2020 (March) Technology introduction COVID-19 Covid Watch becomes the first organization to develop[58] and open source[59][60] an anonymous, decentralized Bluetooth digital contact tracing protocol, publishing their white paper on the subject on 20 March 2020[61][62]
2020 (May 29) Literature Jeffrey P. Kahn publishes Digital Contact Tracing for Pandemic Response: Ethics and Governance Guidance.[63] United States
2020 (July) Concept development Revitalized by the Covid-19 pandemic, the term "contact tracing" is added to the Oxford English Dictionary in their July 2020 update, describing the process of identifying individuals who may have come into contact with someone infected with a disease. The term "contact tracer" is also added, as the term to describe someone who is responsible for identifying those individuals.[20]
2020 Technology introduction It is reported that over 300 academics signed a statement favouring decentralized proximity tracing applications over centralized models, given the difficulty in precluding centralized options being used "to enable unwarranted discrimination and surveillance."[64][65] In a centralized model, a central database records the ID codes of meetings between users. In a decentralized model, this information is recorded on individual phones, with the role of the central database being limited to identifying phones by their ID code when an alert needs to be sent.[66]
2020 Criticism COVID-19 Science writer and sociologist Zeynep Tufekci writes a long piece in The Atlantic on the lack of attention by many public health authorities to the index of dispersion of the SARS-CoV-2 virus and its implications for contact tracing.[67]
2020 Literature Martin Anderson publishes Contact Tracing : Tracking Clinician Resource.[68]
2020 Recommendation COVID-19 German virologist Christian Drosten calls on all citizens of Germany to maintain a diary of their close contacts, in order to facilitate backward tracing and thus help contact tracing teams to find disease clusters.[69] Germany

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See also

External links


  1. 1.0 1.1 1.2 1.3 1.4 1.5 "Contact tracing: how physicians used it 500 years ago to control the bubonic plague". theconversation.com. Retrieved 5 December 2020. 
  2. ""A Menace to the Public Health" — Contact Tracing and the Limits of Persuasion". nejm.org. Retrieved 5 December 2020. 
  3. "REFLECTIONS ON THE HISTORY OF CONTACT TRACING". oneill.law.georgetown.edu. Retrieved 5 December 2020. 
  4. Radcliffe, K; Clarke, J (October 1998). "Contact tracing—where do we go from here?". Sexually Transmitted Infections. 74 (5): 313–314. doi:10.1136/sti.74.5.313. 
  5. "What's it ~really~ like to be a COVID-19 contact tracer". bodyandsoulau. 26 May 2020. Retrieved 22 March 2021. 
  6. 6.0 6.1 6.2 6.3 6.4 6.5 6.6 Müller, Johannes; Kretzschmar, Mirjam (2021). "Contact tracing – Old models and new challenges". Infectious Disease Modelling. 6: 222–231. doi:10.1016/j.idm.2020.12.005. 
  7. "Guidelines for the Implementation and Use of Digital Tools to Augment Traditional Contact Tracing" (PDF). Retrieved 3 March 2021. 
  8. "Privacy-Preserving Contact Tracing". 
  9. "Contact tracing and tracing app". Google Trends. Retrieved 16 April 2021. 
  10. "Contact tracing". books.google.com. Retrieved 19 March 2021. 
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  12. "Bernoulli, Daniel - Encyclopedia of Mathematics". encyclopediaofmath.org. Retrieved 25 March 2021. 
  13. Johnson, Steven (2007). The Ghost Map: The story of London's most terrifying epidemic-- and how it changed science, cities, and the modern world. Riverhead Books. 
  14. Snow, John (1855). On the Mode of Communication of Cholera. John Churchill. 
  15. Rosenberg, Matt. "Map Stops Cholera: John Snow's Map of London." About.com:Geography. N.p., 1 May 2010. http://geography.about.com/cs/medicalgeography/a/cholera.htm. 1 May 2010.
  16. "'Contact tracing' tried and true containing outbreaks | Chickasaw Times". chickasawtimes.net. Retrieved 18 January 2021. 
  17. 17.0 17.1 Mooney, Graham (5 November 2020). ""A Menace to the Public Health" — Contact Tracing and the Limits of Persuasion". New England Journal of Medicine. 383 (19): 1806–1808. ISSN 0028-4793. doi:10.1056/NEJMp2021887. Retrieved 18 January 2021. 
  18. Bender, Ryan; Fuchs, Ashley. "Would COVID-19 digital contact tracing programs violate the Fourth Amendment?". www.law.upenn.edu. Retrieved 18 January 2021. 
  19. Chiavetta, Ryan. "Google, Apple outline privacy considerations for Exposure Notification System". iapp.org. Retrieved 18 January 2021. 
  20. 20.0 20.1 Brooks, Paul (19 October 2020). "Ten Words That Coronavirus Has Added To The Dictionary". Medium. Retrieved 26 March 2021. 
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  25. "Contact tracing's long, turbulent history holds lessons for COVID-19". news.osu.edu. Retrieved 5 December 2020. 
  26. Solomon, Susan Gross. "The Soviet-German Syphilis Expedition to Buriat Mongolia, 1928: Scientific Research on National Minorities". Slavic Review. pp. 204–234. doi:10.2307/2499920. Retrieved 3 March 2021. 
  27. Solomon, Susan Gross (1993). "The Soviet-German Syphilis Expedition to Buriat Mongolia, 1928: Scientific Research on National Minorities". Slavic Review. 52 (2): 204–234. doi:10.2307/2499920. 
  28. DAVIDSON, ROGER. "'Searching for Mary, Glasgow': Contact Tracing for Sexually Transmitted Diseases in Twentieth-Century Scotland". doi:10.1093/shm/9.2.195. 
  29. "Disease detectives: In a public health crisis, contact tracers are on the case". www.endpolio.org. Retrieved 16 March 2021. 
  30. Kampf, Antje (1 April 2008). "A `little world of your own': stigma, gender and narratives of venereal disease contact tracing". Health. 12 (2): 233–250. doi:10.1177/1363459307086845. 
  31. Blom, Ida. "Fighting Venereal Diseases: Scandinavian Legislation c.1800 to c.1950". Medical History. 50 (02): 209–234. doi:10.1017/s0025727300009753. 
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  33. "Coronavirus: Contact tracing and lessons from smallpox in 1962". BBC News. 6 June 2020. Retrieved 16 March 2021. 
  34. McKay, Richard A. (15 August 2016). "Before HIV". Routledge Handbooks Online. doi:10.4324/9781315543420.ch24. 
  35. "Coronavirus: Contact tracing and lessons from smallpox in 1962". BBC News. 6 June 2020. Retrieved 18 January 2021. 
  36. 36.0 36.1 36.2 36.3 36.4 Chen, Yi-Da; Chen, Hsinchun; King, Chwan-Chuen (2011). "Social Network Analysis for Contact Tracing". Infectious Disease Informatics and Biosurveillance: Research, Systems and Case Studies: 339–358. doi:10.1007/978-1-4419-6892-0_15. 
  37. Mai, Thuy (5 May 2015). "Global Positioning System History". NASA. Retrieved 16 April 2021. 
  38. 38.0 38.1 38.2 "History of Contact Tracing: From the Black Death to COVID-19". carebandremembers.com. Retrieved 5 December 2020. 
  39. "How Contact Tracing Helps Mitigate COVID-19 Transmission at WPI". WPI. Retrieved 16 March 2021. 
  40. "What is contact tracing, how could it reduce the spread of COVID-19, and how could it affect me?". www.gavi.org. Retrieved 16 March 2021. 
  41. "How '80s-Era HIV Contact Tracing Can Help Kill COVID". www.advocate.com. 3 July 2020. Retrieved 5 March 2021. 
  42. Clémençon, Stéphan; De Arazoza, Hector; Rossi, Fabrice; Tran, Viet Chi (December 2015). "A statistical network analysis of the HIV/AIDS epidemics in Cuba". Social Network Analysis and Mining. 5 (1): 58. doi:10.1007/s13278-015-0291-z. 
  43. FOWLER, HAYLEY. "From smallpox to HIV, here's how contact tracing helps control outbreaks like COVID-19". miamiherald.com. Retrieved 5 March 2021. 
  44. 44.0 44.1 "Contact tracing most promising approach to lifting Covid-19 lockdown – OECD". Barry And District News. Retrieved 17 April 2021. 
  45. Bahri, Shamshul (2007-01-01). "Enhancing quality of data through automated SARS contact tracing method using RFID technology". International Journal of Networking and Virtual Organisations. 4 (2): 145–162. ISSN 1470-9503. doi:10.1504/IJNVO.2007.013540. 
  46. Altuwaiyan, Thamer; Hadian, Mohammad; Liang, Xiaohui (May 2018). "EPIC: Efficient Privacy-Preserving Contact Tracing for Infection Detection". 2018 IEEE International Conference on Communications (ICC): 1–6. doi:10.1109/ICC.2018.8422886. 
  47. Caldarelli G. (2007). Scale-Free Networks. Oxford University Press.
  48. Keeling, M. J., & Eames, K. T. (2005). Networks and epidemic models. Journal of the Royal Society Interface, 2(4), 295–307.
  49. "Three new cases of influenza A (H1N1), including one domestic case, confirmed in Taiwan; current pandemic alert level in Taiwan raised to phase 3 (yellow light)". 
  50. "The Response to Novel Influenza A (H1N1) Epidemic in Taiwan and Analysis of the Initial 61 Confirmed Cases". 
  51. Farrahi, Katayoun; Emonet, Rémi; Cebrian, Manuel (2014-05-01). "Epidemic Contact Tracing via Communication Traces". PLOS ONE. 9 (5): e95133. ISSN 1932-6203. PMC 4006791Freely accessible. PMID 24787614. doi:10.1371/journal.pone.0095133. 
  52. "Digital contact tracing might be our best shot". 
  53. Xu, Daniel. "Modeling of Network Based Digital Contact Tracing and Testing Strategies for the COVID-19 Pandemic" (PDF). math.mit.edu. 
  54. "Prompt contact tracing disrupts Ebola virus transmission into Senegal". www.healio.com. Retrieved 16 April 2021. 
  55. "Proximity-based trust". patents.google.com. Retrieved 4 December 2020. 
  56. "Speeding up detection to slow down Ebola: Smartphone app is game-changer for contact tracing in hotspots in the Democratic Republic of the Congo". WHO | Regional Office for Africa. Retrieved 20 January 2021. 
  57. "Apple and Google building coronavirus tracking tech for iOS and Android, coming in May". cnet.com. Retrieved 4 December 2020. 
  58. "Covid Watch iOS TCN Testflight App". Apple TestFlight. 2020-03-17. Retrieved 2020-03-17. 
  59. "First implementation of anonymous exposure alert protocol". GitHub. Retrieved 2020-03-17. 
  60. "Covid Watch Github". Github. 2020-03-17. Retrieved 2020-03-17. 
  61. CSGF, DOE (2020-03-31). "Fellow Working to Devise COVID-19 Alert Application". DOE Computational Science Graduate Fellowship. Retrieved 2020-03-31. 
  62. "Private Contact Tracing Protocols Compared: DP-3T and CEN". Zcash Foundation. 2020-04-06. 
  63. Kahn, Jeffrey P.; Technologies, Johns Hopkins Project on Ethics and Governance of Digital Contact Tracing. Digital Contact Tracing for Pandemic Response: Ethics and Governance Guidance. JHU Press. ISBN 978-1-4214-4062-0. 
  64. "Contact Tracing Joint Statement". Retrieved 2020-04-23. 
  65. Hern, Alex (2020-04-20). "Digital contact tracing will fail unless privacy is respected, experts warn". The Guardian. ISSN 0261-3077. Retrieved 4 December 2020. 
  66. "COVID-19". Data notes. Retrieved 4 December 2020. 
  67. "This Overlooked Variable Is the Key to the Pandemic". theatlantic.com. Retrieved 3 December 2020. 
  68. "‎Contact Tracing : Tracking Clinician Resource". books.apple.com. Retrieved 16 April 2021. 
  69. Scharpenberg, Jan (2020-10-13). "Drosten fordert Corona-Tagebuch zur besseren Kontaktnachverfolgung". www.waz.de. Retrieved 4 December 2020.