Humanitarian emergencies, including natural and human-made disasters, conflicts and complex emergencies, constitute what has traditionally been considered the main threat to health security worldwide. Each year millions of people are affected by natural and man-made disasters around the world. Tornados, hurricanes, heavy rains and earthquakes resulted in tens of thousands of deaths and many more affected. Indeed, disasters would not be disastrous if it were not for their effect on the human population. Links between the natural environment and human health have been suggested for centuries. Disasters throughout history have had significant impact on the numbers, health status and life style of populations. It induce: Deaths, Severe injuries, requiring extensive treatments, Increased risk of communicable diseases, Damage to the health facilities, Damage to the water systems, Food shortage, Population movements. The authors focused on the natural disasters, caused by natural forces rather than by acts associated with human behavior and that affect a large population in a widespread geographic region. Describing the general effects of disasters on health, it does not pretend to cover every contingency. Review of recent literature on humanitarian emergencies has shown that the public health consequences of natural disasters are complex. Disasters directly impact the health of the population resulting in physical trauma, acute disease and emotional trauma. In addition, disasters may increase the morbidity and mortality associated with chronic disease and infectious disease through the impact on the health care system.