"Each day disasters occur, and each year millions of people are affected. Whether natural or human-made, the extreme and overwhelming forces of disaster can have far-reaching effects on individual, local community, and national stability. Though disastrous events may last from seconds to a few days, effects on communities and individuals can continue from months to years during the extended process of recovery, reconstruction and restoration. Long-term recovery varies significantly due to the complex interaction of psychological, social, cultural, political, and economic factors. 'A major disaster is defined as any natural catastrophe, or regardless of cause, any fire, flood, or explosion that causes damage of sufficient severity and magnitude to warrant assistance supplementing State, local, and disaster relief organization efforts to alleviate damage, loss, hardship, or suffering'. Events associated with disaster are capable of causing traumatic stress when they cause or threaten death, serious injury, or the physical integrity of individuals. In the event of massive destruction occurring in the United States, a Governor may request a Presidential declaration. This request must satisfy the provisions of the Robert T. Stafford Disaster Relief and Emergency Assistance Act (PL93-288, as amended by PL-100- 707). The Stafford Act provides the authority for the Federal Government to respond to disasters and emergencies in order to provide assistance to save lives and protect public health, safety, and property. High magnitude disasters can overwhelm state medical systems, posing public health threats related to food and water supplies, housing and weather exposure, and injuries."
United States Department of Veterans Affairs, National Center for Posttraumatic Stress Disorder: http://www.ncptsd.va.gov/ncmain/index.jsp