The basic reproductive number of Ebola and the effects of public health measures: the cases of Congo and Uganda

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 R0. Our estimate of R0 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 R0 to quantify its sensitivity to other disease-related parameters. We also analyse 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 2-week delay in their implementation.

An individual-based model of hepatitis A transmission

“…In the absence of any pharmacological interventions, for epidemic outbreaks R 0 can be estimated from notification data during the initial exponential growth phase of the epidemic (Chowell et al, 2004), while for endemic diseases it can be defined as the inverse of the fraction of susceptible individuals at the endemic equilibrium (Anderson and May, 1991).…”

Diagnostic preparedness for infectious disease outbreaks

“…11 This was particularly shown by Chowell and colleagues 12 who estimated that diagnosing 60% of patients with Ebola within one day instead of five days could have dropped the population attack rate from 80% to nearly 0%.…”

Ebola virus disease outbreak in Nigeria: transmission dynamics and rapid control

“…The aim of control interventions is to reduce the net reproduction number R t during an outbreak (also called the effective or instantaneous reproduction number) below unity so that the outbreak eventually ends. Studying the change in R t during the course of an outbreak provides useful information on the effectiveness of the control measures that were implemented (Chowell et al, 2004;Althaus, 2014;Camacho et al, 2014).…”