Disasters are typically categorized as natural or man-made events. Natural disasters, such as floods, tsunamis, and earthquakes, typically have a more extensive impact on population centers, causing more disruption. Hurricane Katrina in 2005 ravaged Louisiana, Mississippi, Alabama, and Florida causing death, numerous casualties, mass evacuations, and disruptions. Natural disasters also include epidemics. In the past, cholera, bubonic plague, and other diseases affected entire continents causing millions of casualties. Today, non-intentional outbreaks and pandemics such as influenza outbreaks and human immunodeficiency virus (HIV) are just two examples of natural disasters that for several reasons can spread quickly, ravaging entire communities. The Spanish flu in the early 1900s caused more than 50 million deaths, and severe acute respiratory syndrome, (SARS) that arose from China in 2003, resulted in thousands of death in that part of the world and concern for a global pandemic. Another virus that afflicts and kills millions of people, particularly in the poor areas of Africa and developing countries, is HIV. It is estimated that from the 1980s, HIV has caused more that 30 million deaths around the world. An estimated 97 % of natural disaster-related deaths occur in developing countries (World Bank, 2000–2001) [2].

Man-made disaster is defined as any event that is caused by the activity of human beings. Explosions, building collapse, civil wars, and nuclear accidents are some examples. The collapse of the Hyatt Regency Hotel in Kansas City in 1981 is one such example. Investigations found that the cause of the collapse was due to an engineering problem. There were more than 100 deaths and more than 200 casualties from that disaster. The transportation industry is commonly involved in incidents that cause large numbers of injured and dead. In 1998 in Eschede, Germany, a high-speed train derailed causing 101 fatalities. Other industrial sectors, such as the chemical industry, have also been involved in man-made catastrophes. In December 1984 in Bhopal, India, more than half a million people were exposed to methyl isocyanate. In the immediate phase after the leak, almost 10,000 people died. The Indian Government has calculated that this event has caused over the years almost 600,000 casualties due to lingering effects of the chemical exposures [3, 4].

The 9/11 terrorist attack in New York and the Oklahoma City bombing (1995) are also man-made disasters. It is important to recognize and underline that disasters also result from war, the conduct of repressive regimes, the use of sanctions, as well as economic and social policies, particularly in developing countries [5]. The Syrian Civil War arose in the 2011 and has caused more than 120,000 deaths and more than 2.3 million refugees since 2013 [6].

Disasters and the response to them follow a pattern called the disaster cycle, which is defined in four phases: mitigation and prevention, preparedness and planning, response and recovery.

Mitigation and prevention involve measures designed either to prevent hazards from occurring or to lessen the effects of the disasters [7]. These measures involve multiple different agencies and commissions, for example, policy-makers introducing regulations regarding the storage, transportation, and disposal of chemical substances. Another example of mitigation is to empower a public health system to monitor and conduct surveillance for infection diseases and at the same time introduce rules regarding health screening at the borders. The importance of the mitigation phase is to avoid disaster or to reduce the impact on the population. It is clear if we compare the 2010 earthquake in Haiti, with a magnitude of 7.0, and similar earthquakes in Japan where despite the same magnitude the number of dead and injured were more limited, that we see the effect of a disaster is often dependent on the underlying condition of the area affected. For decades, Japan has introduced strict building codes that follow seismic regulations. Nevertheless, it is not possible to fully mitigate against all disaster events. For instance, the 2011 earthquake in the Pacific Ocean produced a tsunami that hit the east coast of Japan and caused severe damage, in particular a failure of the nuclear plant in Fukushima, with release of radiation that affected the local community.

The preparedness and planning phase includes all activities conducted on an ongoing basis, in advance of any potential incident. Preparedness involves an integrated combination of assessment; planning; procedures and protocols; training and exercises; personnel qualifications, licensure, and certification; equipment certification; and evaluation and revision [8]. The first step of preparedness is defining what events are more likely to hit a community. The Hazard and Vulnerabilities Assessment (HVA) is a way to objectively risk-stratify those hazards that are more likely to strike a given community. The HVA takes into account different events: natural, man-made, and CBRN (chemical, biologic, radiological, and nuclear). The output from an HVA prioritizes the risks to which a population is most susceptible and should therefore be prepared for. After the HVA, it is possible to then establish standard operating procedures (SOP) and the emergency operations plan (EOP) for the community or hospital. It is a good rule that the EOP adopts an all-hazards approach to preparedness, with annexes and appendices specific for every type of probable event [9]. An important part of the preparedness phase is training. In particular, every healthcare professional must be trained when to activate a disaster response and their own specific roles and responsibilities within the framework of the response. The typical drills commonly used are tabletop and full-scale exercises. They are important also to identify shortfalls, bottlenecks, and gaps in the EOP. The staff should take part in the training, and the EOP should be tested, reviewed, and updated at least once per year.