Modeling suggests COVID-19 outbreaks could be controlled

  • Hellewell J & al.
  • Lancet Glob Health
  • 28 Feb 2020

  • curated by Liz Scherer
  • Clinical Essentials
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Takeaway

  • Modeling data suggest that aggressive contact tracing and case isolation might contain >80% of new COVID-19 outbreaks within 3 months.

Why this matters

  • WHO urges South Asian Region countries to ensure agile, early containment as the virus spreads.
  • Athough the precise COVID-19 transmission characteristics remain unclear, MMWR study findings report SARS-CoV-2 secondary attack rates

Key results

  • At R 0 1.5, median estimate rapidly declined (
  • Control probability declined as initial case numbers increased.
  • At R 0 2.5, >80% of infected contacts needed tracing to achieve 90% control.
  • At R 0 3.5, >90% of contacts needed tracing to achieve 90% control. 
  • Delay from symptom onset to isolation had greatest effect on outbreak control for all reproduction models. 

Study design

  • Mathematical modeling assessing effectiveness of isolation, contact tracing for COVID-19 disease outbreak containment in areas without widespread transmission: (1) initial case numbers, (2) reproduction number (R 0 ), (3) delay in symptom onset to isolation, (4) probability of contacts traced, (5) cases transmitted presymptom onset, (6) subclinical infections.
    • Outbreaks considered contained if transmission ended within 12-16 weeks.
  • Funding: National Institute for Health Research; others.

Limitations

  • Confounders (e.g., control measures) unaccounted for. 
  • Precision bias.