HOW INFECTION SHAPED HISTORY: LESSONS FROM THE IRISH FAMINE.

Human history has been profoundly affected by infection throughout the millennia. In most cases, the impact has been a direct consequence of infection in humans. However, in the 1840s, a plant infection - potato blight, caused by the fungus Phytopthera infestans - showed us how an environmental catastrophe in a vulnerable community can profoundly affect human history. Before the visitation of potato blight, the population of Ireland was the most rapidly growing in Europe in the early 1840s. Yet between 1845 and 1850, Ireland's population fell by over one-third - with 3 million people disappearing from the island - half through death and half through emigration. This directly led to a subsequent diaspora of almost 80 million people, many destined for residence in the Americas. The diaspora carried enormous consequences for the social, economic, and political development of the US. Today, lessons from the Irish famine remain poignant and relevant. Social science maps the dimensions of a disaster dependent on the size of its impact and the relative vulnerability of the society which experiences the disaster. Ireland's vulnerability was in terms of its overall poverty and its dependence on the potato as a subsistence crop. However, a critical factor in the disaster was the political structure in which it occurred - where governance was unwilling and unable to respond to the needs of the population.