The Basic Reproductive Number of Ebola and the Effects of Public Health Measures: The Cases of Congo and Uganda

TL;DR

This study estimates the basic reproductive number of Ebola in Congo and Uganda, demonstrating how timely public health interventions significantly reduce epidemic size through modeling and data analysis.

Contribution

It provides new estimates of Ebola's R0 in two outbreaks and models the impact of intervention timing on epidemic outcomes.

Findings

Estimated R0 of 1.83 for Congo and 1.34 for Uganda.

Interventions halved the final epidemic size compared to delayed actions.

Timely measures significantly reduce Ebola transmission and outbreak magnitude.

Abstract

Despite improved control measures, Ebola remains a serious public health risk in African regions where recurrent outbreaks have been observed since the initial epidemic in 1976. Using epidemic modeling and data from two well-documented Ebola outbreaks (Congo 1995 and Uganda 2000), we estimate the number of secondary cases generated by an index case in the absence of control interventions ($R_0$). Our estimate of $R_0$ is 1.83 (SD 0.06) for Congo (1995) and 1.34 (SD 0.03) for Uganda (2000). We model the course of the outbreaks via an SEIR (susceptible-exposed-infectious-removed) epidemic model that includes a smooth transition in the transmission rate after control interventions are put in place. We perform an uncertainty analysis of the basic reproductive number $R_0$ to quantify its sensitivity to other disease-related parameters. We also analyze the sensitivity of the final epidemic size to the time interventions begin and provide a distribution for the final epidemic size. The control measures implemented during these two outbreaks (including education and contact tracing followed by quarantine) reduce the final epidemic size by a factor of 2 relative the final size with a two-week delay in their implementation.