Beyond the terrible toll in human lives and suffering, the Ebola epidemic currently afflicting West Africa is already having a measurable economic impact in terms of forgone output; higher fiscal deficits; rising prices; lower real household incomes and greater poverty. These economic impacts include the costs of healthcare and forgone productivity of those directly affected but, more importantly, they arise from choices by others to avoid exposure to the disease, called 'aversion behaviour'. This report provides a systematic analysis of the channels of economic impact and the likely magnitude of that impact for Guinea, Liberia, and Sierra Leone, as well as West Africa as a whole. The short-term (2014) impact of Ebola on economic output is on the order of US$359 million in foregone output in 2013 prices. Two alternative scenarios are used to estimate the medium-term (2015) impact of the epidemic. A 'Low Ebola' scenario corresponds to rapid containment within the three most severely affected countries, while 'High Ebola' corresponds to slower containment in the core three countries, with some broader regional contagion. The estimates of the GDP lost as a result of the epidemic in the core three countries for 2015 alone sum to US$97 million under Low Ebola (implying some recovery from 2014), and US$809 million under High Ebola (in 2013 dollars). Over the medium term, however, both epidemiological and economic contagion in the broader sub-region of West Africa is likely. This report uses a multi-country general equilibrium model to estimate the medium-term impact on output for West Africa as a whole. Under Low Ebola, the loss in GDP for the sub-region is estimated to be US$2.2 billion in 2014 and US$1.6 billion in 2015. Under High Ebola, the estimates are US$7.4 billion in 2014, and US$25.2 billion in 2015. This analysis shows that the economic impacts are already very serious in the core three countries - particularly Liberia and Sierra Leone - and could become catastrophic under a slow-containment, High Ebola scenario. In broader regional terms, the economic impacts could be limited if immediate national and international responses succeed in containing the epidemic and mitigating aversion behavior. If, on the other hand, the epidemic spreads into neighboring countries, some of which have much larger economies, the cumulative two-year impact could reach US$32.6 billion by the end of 2015 - almost 2.5 times the combined 2013 GDP of the core three countries.