This paper explores the implications of a pandemic influenza outbreak on the global economy through a range of scenarios (mild, moderate, severe, and ultra) that span the historical experience of influenza pandemics of the twentieth century. An influenze pandemic would be expected to lead to: a fall in the labour force to different degrees in different countries due to a rise in mortality and illness; an increase in the cost of doing business; a shift in consumer preferences away from exposed sectors; and a re-evealuation of country risk as investors observe the responses of governments. The paper finds that even a mild pandemic has significant consequences for global economic output. The mild scenario is estimated to cost the world 1.4 million lives and close to 0.8% of GDP (approximately $US330 billion) in lost economic output. As the scale of the pandemic increases, so do the economic costs. A massive global economic slowdown occurs in the “ultra” scenario with over 142.2 million people killed and a GDP loss of $US4.4 trillion. The composition of the slowdown differs sharply accross countries with a major shift of global capital from the affected economies to the less affected safe haven economies of North America and Europe.