Disasters can be divided into two broad categories - those triggered by natural phenomena such as earthquakes, volcanic eruptions, hurricanes, floods. - Those caused by human intervention, war, violence, terrorism, massive accidents, chemical and nuclear accidents, etc. Complex emergencies usually involve situations in which people suffer accidents and loss of property, basic services and livelihoods as a result of war, civil strife or other political conflicts in alarming rise in the world. In many cases people are forced to leave their homes temporarily or permanently, others become refugees in other countries. In technological disasters, large numbers of people are directly affected by major industrial accidents, severe pollution incidents, nuclear downloads unplanned, large fires, explosions, hazardous substances, etc. There is a connection that should always be taken into account between natural disasters and those caused by man, that can trigger secondary disasters - a fire after an earthquake, environmental contamination after a flood - that explore individual and community vulnerability.
In developing countries there are factors contributing to the occurrence and severity of disasters and their consequences: poverty and social inequity. Unequal access to basic services and health services. Environmental degradation due to misuse of land. Rapid population growth without family planning measures or adequate urban. Health hazards and currently have enough information about the causes and nature of disasters, and populations at risk. This knowledge allows us to anticipate some of the effects of disasters on the health of affected communities from the health perspective, disasters are defined by their impact on welfare biopsychosocial people The health consequences of disasters go far beyond what conventional indicators reveal about deaths and injuries and their impact is not only considered initially.