Bidirectional contact tracing dramatically improves COVID-19 control

Contact tracing is critical to controlling COVID-19, but most protocols only “forward-trace” to notify people who were recently exposed. Using a stochastic branching-process model, we show that “bidirectional” tracing to identify infector individuals and their other infectees robustly improves outbreak control, reducing the effective reproduction number (Reff) by at least ∼0.3 while dramatically increasing resilience to low case ascertainment and test sensitivity. Adding smartphone-based exposure notification can further reduce Reff by 0.25, but only if nearly all smartphones can detect exposure events. Our results suggest that with or without digital approaches, implementing bidirectional tracing will enable health agencies to control COVID-19 more effectively without requiring high-cost interventions.

[1]  Elissa M. Redmiles,et al.  Americans' willingness to adopt a COVID-19 tracking app The role of app distributor , 2020, First Monday.

[2]  A. Kucharski,et al.  Estimating the overdispersion in COVID-19 transmission using outbreak sizes outside China , 2020, Wellcome open research.

[3]  D. Patrick,et al.  High SARS-CoV-2 Attack Rate Following Exposure at a Choir Practice - Skagit County, Washington, March 2020. , 2020, MMWR. Morbidity and mortality weekly report.

[4]  Hsien-Ho Lin,et al.  Contact Tracing Assessment of COVID-19 Transmission Dynamics in Taiwan and Risk at Different Exposure Periods Before and After Symptom Onset , 2020, JAMA internal medicine.

[5]  A. Vespignani,et al.  Changes in contact patterns shape the dynamics of the COVID-19 outbreak in China , 2020, Science.

[6]  R. Geskus,et al.  The natural history and transmission potential of asymptomatic SARS-CoV-2 infection , 2020, medRxiv.

[7]  Mark S. Anderson,et al.  Test performance evaluation of SARS-CoV-2 serological assays , 2020, medRxiv.

[8]  Hannah Fry,et al.  Effectiveness of isolation, testing, contact tracing, and physical distancing on reducing transmission of SARS-CoV-2 in different settings: a mathematical modelling study , 2020, The Lancet Infectious Diseases.

[9]  E. Lavezzo,et al.  Suppression of COVID-19 outbreak in the municipality of Vo, Italy , 2020, medRxiv.

[10]  L. Fang,et al.  Household Secondary Attack Rate of COVID-19 and Associated Determinants , 2020, medRxiv.

[11]  S. Merler,et al.  Epidemiological characteristics of COVID-19 cases in Italy and estimates of the reproductive numbers one month into the epidemic , 2020, medRxiv.

[12]  W. Wei,et al.  Presymptomatic Transmission of SARS-CoV-2 — Singapore, January 23–March 16, 2020 , 2020, MMWR. Morbidity and mortality weekly report.

[13]  C. Faes,et al.  Estimating the generation interval for coronavirus disease (COVID-19) based on symptom onset data, March 2020 , 2020, Euro surveillance : bulletin Europeen sur les maladies transmissibles = European communicable disease bulletin.

[14]  M. Wang,et al.  Epidemiological parameters of coronavirus disease 2019: a pooled analysis of publicly reported individual data of 1155 cases from seven countries , 2020, medRxiv.

[15]  Kai Kupferschmidt,et al.  Countries test tactics in 'war' against COVID-19. , 2020, Science.

[16]  L. Meyers,et al.  Serial Interval of COVID-19 among Publicly Reported Confirmed Cases , 2020, Emerging infectious diseases.

[17]  Eric H. Y. Lau,et al.  Temporal dynamics in viral shedding and transmissibility of COVID-19 , 2020, Nature Medicine.

[18]  Ruiyun Li,et al.  Substantial undocumented infection facilitates the rapid dissemination of novel coronavirus (SARS-CoV-2) , 2020, Science.

[19]  Lucie Abeler-Dörner,et al.  Quantifying SARS-CoV-2 transmission suggests epidemic control with digital contact tracing , 2020, Science.

[20]  Jianping Huang,et al.  Indirect Virus Transmission in Cluster of COVID-19 Cases, Wenzhou, China, 2020 , 2020, Emerging infectious diseases.

[21]  Marc Lipsitch,et al.  Comparative Impact of Individual Quarantine vs. Active Monitoring of Contacts for the Mitigation of COVID-19: a modelling study , 2020, medRxiv.

[22]  M. Kretzschmar,et al.  Effectiveness of Isolation and Contact Tracing for Containment and Slowing Down a COVID-19 Epidemic: A Modelling Study , 2020, Social Science Research Network.

[23]  P. Klepac,et al.  Feasibility of controlling COVID-19 outbreaks by isolation of cases and contacts , 2020, The Lancet Global Health.

[24]  Lei Liu,et al.  Antibody responses to SARS-CoV-2 in patients of novel coronavirus disease 2019 , 2020, medRxiv.

[25]  Jian-ming Wang,et al.  Clinical characteristics of 24 asymptomatic infections with COVID-19 screened among close contacts in Nanjing, China , 2020, Science China Life Sciences.

[26]  Hannah R. Meredith,et al.  The incubation period of 2019-nCoV from publicly reported confirmed cases: estimation and application , 2020 .

[27]  Johannes Müller,et al.  The effect of delay on contact tracing. , 2016, Mathematical biosciences.

[28]  P. Read,et al.  Contact tracing using provider referral: how difficult is it? , 2013, Sexual health.