Alliance for Pandemic Preparedness

February 12, 2020

Beyond R0: the importance of contact tracing when predicting epidemics



  • Hebert-Dufrense, et al. apply network theory to improve basic estimates of R0, using added information from the numeric heterogeneity of secondary infections – that is, the fact that some individuals create more secondary infections then others. 
  • A range of predictions for the final size of the Wuhan 2019-nCoV epidemic is provided, using R0 estimates from early cases and SARS data for the underlying distribution of secondary cases. The resulting range, as a fraction of the total susceptible population, is 5%-40%. 
  • With a high heterogeneity (e.g., transmission mostly maintained by “super-spreading” events), the epidemic is less likely to spread extensively and be easier to manage with contact tracing, screening and infection control 
  • With low heterogeneity, containment strategies will likely fail, and pandemic of 2019-nCoV is likely.
  • Overall, this network modeling approach highlights the need for contact tracing during emerging infectious disease outbreaks; and the need to look beyond R0 when predicting epidemic size.

Hebert-Dufrense L, et al. (Feb 11, 2020) Beyond R0: the importance of contact tracing when predicting epidemics. Pre-print. Accessed Feb 12 from