Feasibility of controlling COVID-19 outbreaks by isolation of cases and contacts

By J. Hellewell, S. Abbott, A. Gimma, N. Bosse, C. Jarvis, T. Russell, J. Munday, A. Kucharski, W. Edmunds, F. Sun and 12 more. Lancet Global Health, 2020

2,366 citations recorded by the source corpus.

Background Isolation of cases and contact tracing is used to control outbreaks of infectious diseases, and has been used for coronavirus disease 2019 (COVID-19). Whether this strategy will achieve control depends on characteristics of both the pathogen and the response. Here we use a mathematical model to assess if isolation and contact tracing are able to control onwards transmission from imported cases of COVID-19. Methods We developed a stochastic transmission model, parameterised to the COVID-19 outbreak. We used the model to quantify the potential effectiveness of contact tracing and isolation of cases at controlling a severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2)-like pathogen. We considered scenarios that varied in the number of initial cases, the basic reproduction number (R0), the delay from symptom onset to isolation, the probability that contacts were traced, the proportion of transmission that occurred before symptom onset, and the proportion of subclinical infections. We assumed isolation prevented all further transmission in the model. Outbreaks were deemed controlled if transmission ended within 12 weeks or before 5000 cases in total. We measured the success of controlling outbreaks using isolation and contact tracing, and quantified the weekly maximum number of cases traced to measure feasibility of public health effort. Findings Simulated outbreaks starting with five initial cases, an R0 of 1·5, and 0% transmission before symptom onset could be controlled even with low contact tracing probability; however, the probability of controlling an outbreak decreased with the number of initial cases, when R0 was 2·5 or 3·5 and with more transmission before symptom onset. Across different initial numbers of cases, the majority of scenarios with an R0 of 1·5 were controllable with less than 50% of contacts successfully traced. To control the majority of outbreaks, for R0 of 2·5 more than 70% of contacts had to be traced, and for an R0 of 3·5 more than 90% of contacts had to be traced. The delay between symptom onset and isolation had the largest role in determining whether an outbreak was controllable when R0 was 1·5. For R0 values of 2·5 or 3·5, if there were 40 initial cases, contact tracing and isolation were only potentially feasible when less than 1% of transmission occurred before symptom onset. Interpretation In most scenarios, highly effective contact tracing and case isolation is enough to control a new outbreak of COVID-19 within 3 months. The probability of control decreases with long delays from symptom onset to isolation, fewer cases ascertained by contact tracing, and increasing transmission before symptoms. This model can be modified to reflect updated transmission characteristics and more specific definitions of outbreak control to assess the potential success of local response efforts. Funding Wellcome Trust, Global Challenges Research Fund, and Health Data Research UK.

Subfields: Infectious Diseases, Information Systems, Modeling and Simulation

View Paper: https://www.semanticscholar.org/paper/75ecf969ce1be6f05fef55c8ea7d38e12ec7f7f5

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Citations in the corpus

Insights into SARS-CoV-2 genome, structure, evolution, pathogenesis and therapies: Structural genomics approach (2020, positive): “6, which means that the infected cases grow at an exponential rate [10].”
Spread and dynamics of the COVID-19 epidemic in Italy: Effects of emergency containment measures (2020, background): “Their effective implementation is generally a matter of concern (38).”
Modelling the COVID-19 epidemic and implementation of population-wide interventions in Italy (2020, methodology): “Our simulation results, achieved by combining the model with the available data about the COVID-19 epidemic in Italy, suggest the urgent need – and the effectiveness – of strong social-distancing measures, in line with [2, 24, 26].”
Temporal dynamics in viral shedding and transmissibility of COVID-19 (2020, background): “16 is the author/funder, who has granted medRxiv a license to display the preprint in (which was not certified by peer review) preprint ”
Quantifying SARS-CoV-2 transmission suggests epidemic control with digital contact tracing (2020, background): “We acknowledge that boundaries between these categories may be blurred, but defined broadly these categories have different implications for prevention, responding differently to classical measures of case isolation and quarantining contacts (9, 10) [for a specific application to COVID-19, see below”
Face masks for the public during the covid-19 crisis (2020, background): “23 The suggestion that the public should not wear masks because healthcare workers need them more is valid up to a point, but it is surely an argument for manufacturing more masks, not for denying them to populations who could potentially benefit from them.”
Microbial Colonization and Degradation of Microplastics in Aquatic Ecosystem: A Review (2021, background): “In 2020 due to the COVID-19 pandemic (Hellewell et al. 2020), an abrupt increase in plastic pollution from the use of sanitizers, masks, gloves, PPE kits, saline bottles, and many other health care products and equipment is threatening our aquatic environment.”
Leveraging Data Science to Combat COVID-19: A Comprehensive Review (2020, background): “This approach has been seemingly successful in containing the outbreak [85].”