Post-death Transmission of Ebola: Challenges for Inference and Opportunities for Control
Abstract
Multiple epidemiological models have been proposed to predict the spread of
Ebola in West Africa. These models include consideration of counter-measures
meant to slow and, eventually, stop the spread of the disease. Here, we examine
one component of Ebola dynamics that is of growing concern -- the transmission
of Ebola from the dead to the living. We do so by applying the toolkit of
mathematical epidemiology to analyze the consequences of post-death
transmission. We show that underlying disease parameters cannot be inferred
with confidence from early-stage incidence data (that is, they are not
"identifiable") because different parameter combinations can produce virtually
the same epidemic trajectory. Despite this identifiability problem, we find
robustly that inferences that don't account for post-death transmission tend to
underestimate the basic reproductive number -- thus, given the observed rate of
epidemic growth, larger amounts of post-death transmission imply larger
reproductive numbers. From a control perspective, we explain how improvements
in reducing post-death transmission of Ebola may reduce the overall epidemic
spread and scope substantially. Increased attention to the proportion of
post-death transmission has the potential to aid both in projecting the course
of the epidemic and in evaluating a portfolio of control strategies.