2014 Ebola Outbreak: Media Events Track Changes in Observed Reproductive Number

Commentary The ongoing Ebola epidemic in West Africa is significantly larger and more widespread than any other in history. While previous outbreaks in small villages have burned out due to the local depletion of susceptible individuals, this epidemic has spread across entire countries, and thus can only be curtailed by interventions aimed at reducing new infections across all locations.1 The efficacy of large-scale interventions for an Ebola epidemic of this scale has not yet been studied. Here, we describe the relationship between various media reported events – including interventions – and changes in epidemic behavior between April 14 and October 11, 2014 in Sierra Leone and Liberia. Using WHO aggregate reporting data,2,3 we estimated observed reproductive number (RObs) over time for Sierra Leone and Liberia using the Incidence Decay and Exponential Adjustment (IDEA) method.4 This was achieved by optimizing both R0 and d over 10 serial intervals using the GRG non-linear algorithm, where the objective function was set to minimize the sum of square differences between modeled cumulative incidence and actual cumulative incidence data from the WHO. We defined the observed reproductive number as follows: Which describes the observed number of secondary infections per infected individual for a given serial interval (t), defined as an integer value equal to the disease incubation period plus one half of the illness duration. Using HealthMap (healthmap.org), we identified n...
Source: PLOS Currents Outbreaks - Category: Epidemiology Authors: Source Type: research