Estimating the reproduction number of Ebola virus (EBOV) during the 2014 outbreak in West Africa

TL;DR

This study estimates the Ebola virus's reproduction number during the 2014 West Africa outbreak using an SEIR model, providing insights into transmission dynamics and the impact of control measures in Guinea, Sierra Leone, and Liberia.

Contribution

It applies an SEIR model to recent outbreak data to estimate reproduction numbers and assess control efforts' effectiveness in different countries.

Findings

Estimated basic reproduction numbers: Guinea 1.51, Sierra Leone 2.53, Liberia 1.59.

Control measures appeared effective in Guinea and Sierra Leone by mid-2014.

No decline in Liberia's effective reproduction number by late August 2014.

Abstract

The 2014 Ebola virus (EBOV) outbreak in West Africa is the largest outbreak of the genus Ebolavirus to date. To better understand the spread of infection in the affected countries, it is crucial to know the number of secondary cases generated by an infected index case in the absence and presence of control measures, i.e., the basic and effective reproduction number. In this study, I describe the EBOV epidemic using an SEIR (susceptible-exposed-infectious-recovered) model and fit the model to the most recent reported data of infected cases and deaths in Guinea, Sierra Leone and Liberia. The maximum likelihood estimates of the basic reproduction number are 1.51 (95% confidence interval [CI]: 1.50-1.52) for Guinea, 2.53 (95% CI: 2.41-2.67) for Sierra Leone and 1.59 (95% CI: 1.57-1.60) for Liberia. The model indicates that in Guinea and Sierra Leone the effective reproduction number might have dropped to around unity by the end of May and July 2014, respectively. In Liberia, however, the model estimates no decline in the effective reproduction number by end-August 2014. This suggests that control efforts in Liberia need to be improved substantially in order to stop the current outbreak.