Objective Contact tracing is a central public health response to infectious disease outbreaks, especially in the early stages of an outbreak when specific treatments are limited. Importation of novel coronavirus (COVID-19) from China and elsewhere into the UK highlights the need to understand the impact of contact tracing as a control measure.
Design Detailed survey information on social encounters from over 5800 respondents is coupled to predictive models of contact tracing and control. This is used to investigate the likely efficacy of contact tracing and the distribution of secondary cases that may go untraced.
Results Taking recent estimates for COVID-19 transmission we predict that under effective contact tracing less than 1 in 6 cases will generate any subsequent untraced infections, although this comes at a high logistical burden with an average of 36 individuals traced per case. Changes to the definition of a close contact can reduce this burden, but with increased risk of untraced cases; we find that tracing using a contact definition requiring more than 4 hours of contact is unlikely to control spread.
Conclusions The current contact tracing strategy within the UK is likely to identify a sufficient proportion of infected individuals such that subsequent spread could be prevented, although the ultimate success will depend on the rapid detection of cases and isolation of contacts. Given the burden of tracing a large number of contacts to find new cases, there is the potential the system could be overwhelmed if imports of infection occur at a rapid rate.
- communicable diseases
- Disease modeling
- public health policy
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Contributors Conceptualisation: TDH, JMR, MJK. Writing the manuscript: MJK, JMR, TDH. Data curation: JMR, MJK. Methodology and software: MJK.
Funding MJK is supported by the Engineering and Physical Sciences Research Council (EP/S022244/1) and the Health Data Research UK, which receives its funding from HDR UK Ltd (NIWA1). TDH acknowledges support from the Li Ka Shing Foundation. JMR acknowledges support from the Medical Research Council (MR/5004793/1) and the Engineering and Physical Sciences Research Council (EP/N014499/1). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.
Competing interests None declared.
Patient consent for publication Not required.
Data sharing statement Data are available in a public, open access repository.
Provenance and peer review Not commissioned; externally peer reviewed.
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