"The term disaster usually evokes images of massive material damage and great human distress caused by some swift catastrophe. In offering a more rigorous definition, a leading sociologist has defined a disaster as a sudden event that disrupts the social structure, and prevents execution of some or all of its essential functions. Commonly, disasters caused by natural forces or events are distinguished from those that man brings upon himself. With one exception, the disasters examined in this study are natural, though they may have been provoked or exacerbated by human customs or follies. Specifically, the study examines how Army medical personnel have responded to such events and shows how they aided disrupted civil societies or communities by furnishing health care. Studies of disaster relief usually focus on fires, floods, storms, and earthquakes. Two other types of calamities- famines and epidemics- are included here. Such happenings are in truth disasters since they disrupt the social structure and interrupt some of its essential functions. They often occur as direct results of natural upheavals or of war, and a story of medical assistance that excluded them would obviously be incomplete. Significant changes in the response to disaster have developed over the past two centuries. Disasters of all types awed early Americans, who did not understand their causes; settle interpreted disaster as a supernatural message, while others sought an elusive natural explanation, Since the eighteenth century, the search for causes has revealed disasters to be understandable natural occurrences that scientists have tried with increasing sophistication to explain, predict, and- especially for epidemics- prevent."
Office of Medical History - Office of the Surgeon General: http://history.amedd.army.mil/default_index2.html