Real-time estimation of R_0 for supporting public-health policies against COVID-19

Contreras, S.; Villavicencio, H. A.; Medina-Ortiz, D.; Saavedra, C. P.; Olivera-Nappa, A.

Background: In the absence of a consensus protocol to slow down the current SARS- CoV2 spread, policy makers are in need of real-time indicators to support decisions in public health matters. The Basic Reproduction Number (R_0) represents viral spread rate and can be dramatically modified by the application of effective public control measures. However, current methodologies to calculate R_0 from data remain cumbersome and unusable during an outbreak. Objective: To provide a simple mathematical formulation for obtaining R_0 in Real-Time, and apply it to assess the effectiveness of public-health policies in different iconic countries. Study design: By modifying the equations describing the spread of the virus, we derived a real-time $R_0$ estimator that can be readily calculated from daily official case reports. Results: We show the application of a time trend analysis of the R_0 estimator to assess the efficacy and promptness of public health measures that impacted on the development of the COVID-19 epidemic in iconic countries. Conclusions: We propose our simple estimator and method as useful tools to follow and assess in real time the effectiveness of public health policies on COVID-19 evolution.