Bidirectional contact tracing is required for reliable COVID-19 control

@article{Bradshaw2020BidirectionalCT,
  title={Bidirectional contact tracing is required for reliable COVID-19 control},
  author={William J. Bradshaw and Ethan C. Alley and Jonathan Huggins and Alun L. Lloyd and Kevin M. Esvelt},
  journal={medRxiv},
  year={2020}
}
Contact tracing is critical to limiting the spread of pandemics such as COVID-19, but most protocols only "forward-trace" to notify people who were recently exposed. Using a stochastic branching process model, we find that "bidirectional" tracing to identify infector individuals robustly outperforms forward-only approaches across a wide range of scenarios. The addition of rapid smartphone-based exposure notification offers few benefits over conventional manual tracing alone unless uptake of the… 
Effect of manual and digital contact tracing on COVID-19 outbreaks: a study on empirical contact data
TLDR
It is found that the obtained reduction of epidemic size has a robust behavior: this benefit is linear in the fraction of contacts recalled during MCT, and quadratic in the app adoption, with no threshold effect.
Implication of backward contact tracing in the presence of overdispersed transmission in COVID-19 outbreaks.
TLDR
Backward contact tracing can be an effective tool for outbreak control, especially in the presence of overdispersion as was observed with SARS-CoV-2.
Implication of backward contact tracing in the presence of overdispersed transmission in COVID-19 outbreaks.
TLDR
Backward contact tracing can be an effective tool for outbreak control, especially in the presence of overdispersion as is observed with SARS-CoV-2.
Implication of backward contact tracing in the presence of overdispersed transmission in COVID-19 outbreaks
TLDR
Backward contact tracing can be an effective tool for outbreak control, especially in the presence of overdispersion as is observed with SARS-CoV-2.
Effect of manual and digital contact tracing on COVID-19 outbreaks: a study on empirical contact data
TLDR
Benefits are higher and the cost lower if the epidemic reproductive number is lower, showing the importance of combining tracing with additional mitigation measures, and the observed phenomenology is qualitatively robust across datasets and parameters.
Using real-world contact networks to quantify theeffectiveness of digital contact tracing and isolation strategies for Covid-19 pandemic
TLDR
It is found that restrictive policies are more effective in confining the epidemics but come at the cost of quarantining a large part of the population with a consequent social cost, and strategies focusing on long exposure times, even for weak links, perform better than approaches that emphasize close-range contacts for shorter time-periods.
Implication of backward contact tracing in the presence of overdispersed transmission in COVID-19 outbreak
TLDR
This work explored the potential of combining backward contact tracing with more conventional forward contact tracing for control of COVID-19 by using a simple branching process model.
COVID-19 mitigation by digital contact tracing and contact prevention (app-based social exposure warnings)
TLDR
Results show that contact prevention remains effective in scenarios with high diagnostic/response time delays and low infection detection rates, which greatly impair the effect of traditional contact tracing strategies.
The effectiveness of backward contact tracing in networks.
TLDR
It is shown that strategically executed contact tracing can prevent a substantial fraction of transmissions with a higher efficiency-in terms of prevented cases per isolation-than case isolation alone.
COVID-19 risk evaluation and testing strategies based on contact tracing network and information analysis
TLDR
A systematic strategy is proposed to determine the risk profile of all the individuals in the community by incorporating serial and parallel pathways of the infection transmission considering multiple steps of transmission, and shows that in general, information increases with an increase in the group size.
...
1
2
3
...

References

SHOWING 1-10 OF 47 REFERENCES
Quantifying SARS-CoV-2 transmission suggests epidemic control with digital contact tracing
TLDR
A mathematical model for infectiousness was developed to estimate the basic reproductive number R0 and to quantify the contribution of different transmission routes and the requirements for successful contact tracing, and the combination of two key parameters needed to reduce R0 to less than 1 was determined.
Effectiveness of isolation, testing, contact tracing and physical distancing on reducing transmission of SARS-CoV-2 in different settings
TLDR
This analysis estimates that a high proportion of cases would need to self-isolate and a highportion of their contacts to be successfully traced to ensure an effective reproduction number that is below one in the absence of other measures.
Contact Tracing Assessment of COVID-19 Transmission Dynamics in Taiwan and Risk at Different Exposure Periods Before and After Symptom Onset
TLDR
High transmissibility of COVID-19 before and immediately after symptom onset suggests that finding and isolating symptomatic patients alone may not suffice to interrupt transmission, and that more generalized measures might be required, such as social distancing.
Effectiveness of Isolation and Contact Tracing for Containment and Slowing Down a COVID-19 Epidemic: A Modelling Study
TLDR
Isolation and contact tracing can be an effective means to control early epidemics, but only if transmissibility as measured by R0 is in the lower ranges of reported values.
Changes in contact patterns shape the dynamics of the COVID-19 outbreak in China
TLDR
It is found that social distancing alone, as implemented in China during the outbreak, is sufficient to control COVID-19, and children 0 to 14 years of age are less susceptible to severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection.
Temporal dynamics in viral shedding and transmissibility of COVID-19
TLDR
It is estimated that 44% (95% confidence interval, 25–69%) of secondary cases were infected during the index cases’ presymptomatic stage, in settings with substantial household clustering, active case finding and quarantine outside the home.
Estimating the overdispersion in COVID-19 transmission using outbreak sizes outside China
TLDR
The finding of a highly-overdispersed offspring distribution of COVID-19 highlights a potential benefit to focusing intervention efforts on superspreading, as most infected individuals do not contribute to the expansion of an epidemic, the effective reproduction number could be drastically reduced.
Household Secondary Attack Rate of COVID-19 and Associated Determinants
TLDR
SARS-CoV-2 is more transmissible in households than SARS- coV and MERS-coV, and the elderly ≥60 years old are the most vulnerable to household transmission.
Comparative Impact of Individual Quarantine vs. Active Monitoring of Contacts for the Mitigation of COVID-19: a modelling study
TLDR
This model suggests that individual quarantine in high feasibility settings where at least three-quarters of infected contacts are individually quarantined contains an outbreak of COVID-19 with a short serial interval 84% of the time, and when resources are prioritized for scalable interventions such as social distancing, it shows active monitoring or individual quarantine of high-risk contacts can contribute synergistically to mitigation efforts.
...
1
2
3
4
5
...