  In 2014, a major epidemic of human Ebola virus disease emerged in West
Africa, where human-to-human transmission has now been been sustained for
greater than 10 months. In the summer of 2014, there was great uncertainty
about the answers to several key policy questions concerning the path to
containment. In recent years, epidemic models have been used to guide public
health interventions. But, model-based policy relies on high quality causal
understanding of transmission, including the availability of appropriate
dynamic transmission models and reliable reporting about the sequence of case
incidence for model fitting, which were lacking for this epidemic. To
investigate the range of potential transmission scenarios, we developed a
multi-type branching process model that incorporates key heterogeneities and
time-varying parameters to reflect changing human behavior and deliberate
interventions. Ensembles of this model were evaluated at a set of parameters
that were both epidemiologically plausible and capable of reproducing the
observed trajectory. Results suggest that epidemic outcome depends on both
hospital capacity and individual behavior. The model predicts that if hospital
capacity is not increased soon, then transmission may outpace the rate of
isolation and the ability to provide care for the ill, infectious, and dying.
Similarly, containment will probably require individuals to adopt behaviors
that increase the rates of case identification and isolation and secure burial
of the deceased. Given current knowledge, it is uncertain that this epidemic
will be contained even with 99% hospitalization rate at the currently projected
hospital capacity.
