The Rescue Stage - Disruption of the Infrastructure Critical To Public Health and Welfare. The critical infrastructure of a community is vital to both the well being and public health of its members. As mentioned above, the critical infrastructure constitutes a variety of systems including shelter, power grids, fuel lines, the supply of potable water, transportation networks, and communication systems. Disruption of these services can have immediate effects, as well as long-term consequences. After providing appropriate and timely emergency medical care, the next priority for the survivors of a natural disaster is shelter. Shelter is a basic human need that protects individuals against the elements, and secondly allows for the restoration of proper public health practices that will protect against long-term health consequences. Finding appropriate shelter for all victims usually becomes a priority around the 48-hour mark after a disaster. At this stage the rescue operation is most likely continuing. For the survivors, however, the recovery and even the reconstruction stage must begin. Loss of shelter is one of the most common consequences of a natural disaster. While different types of natural disasters disrupt the community in different ways, a common thread is their ability to force people from their homes. In an earthquake, tornado, fire, or a severe winter storm, loss of shelter due to collapsed or unsafe structures leaves victims homeless until other permanent structures can be completed. In disasters such as a hurricane or flood, many displaced victims may be able to return to their homes after the disaster has passed. The type and longevity of the shelter that needs to be provided depends on the particular situation at hand. Damage to power grids and fuel lines can have far reaching consequences. As exemplified in the severe winter storm to hit the eastern United States and Canada in 1998, an extended disruption in the power grid can leave homeowners vulnerable to the extreme cold as well as disrupt most forms of communication. As days without power turns into weeks, many public health issues arise. Many individuals not only loose their ability to heat or cool their homes, but they also loose the ability to adequately refrigerate or prepare food. The spoilage of food can exacerbate existing food shortages leading to possible large-scale malnutrition. Additionally, in a power outage many households use candles at night and portable kerosene or gas heaters. This increases the risk of fire and/or carbon dioxide poisoning dramatically.In other disasters, such as a tornado or a hurricane, the loss of power can also disable automatic warning systems, thereby increasing a community's vulnerability to the disaster's destructive affects. Finally, many communities require an adequate electricity supply in order to properly treat or pump their drinking water. With an extended complete power outage, drinking water that is able to reach homes runs the risk of becoming contaminated. This is compounded with the fact that individuals lack the ability to conveniently boil the water that they do receive. The loss of a potable water supply is one of the most devastating long-term effects from a natural disaster. As mentioned above, water supplies can be contaminated due to a failure of treatment facilities. However, in earthquakes, the water supply can additionally become contaminated due to damaged water mains. In floods and hurricanes, filtration systems can become overwhelmed and water basins can be rendered impure by floodwaters containing debris and toxins. In volcanic eruptions, acid rain formed from ash clouds can pollute the entire water cycle. The lack of drinkable water in a community quickly leads to water borne illness and dehydration. As personal hygiene decreases, disease can become more frequent and more difficult to contain. Finally, a lack of water due either to pump failure or broken water mains can lead hinder fire fighting efforts, allowing small fires to get out of control and devastate an entire urban centre. An interruption of an area's transportation network not only hinders emergency vehicle response time, but can also delay or prevent the delivery of food, medicine, external aid and other essential reconstruction supplies. Island communities are extremely vulnerable to isolation as bridges and tunne ls connecting to the mainland represent high value access points, which if closed can leave a large population stranded. Additionally, severe weather that commonly accompanies a natural disaster may prevent safe passage over water or by air. Likewise, remote communities which are only accessible through key mountain passes or long jungle roads are vulnerable to isolation from external aid in the event of a severe natural disaster such as land slides, flooding, or earthquakes. A final aspect of a community's critical infrastructure that a natural disaster may disrupt is the area's communication network. An organised response and revitalization effort needs a stable and comprehensive communication network in order to be both effective and efficient. In order to facilitate a quick recovery, specific sites within the disaster area need to be able to request resupply in response to the needs they are faced with. As a disaster situation changes and matures, the site needs will develop as well. A suitable communication system is vital to the proper integration of a multi-organisational response with the relay of information to and from field command posts to an emergency operations centre. Note that field command posts are usually located at the disaster and are responsible for the emergency rescue operations that occur on site. Meanwhile, an emergency operations centre is usually located distant to the actual disaster site, near governmental offices or supply stockpiles. An emergency operation centre is concerned with the accurate and efficient distribution of rescue supplies to all areas of the disaster in order to save the most lives and minimise any subsequent damage. During a communication disruption, the loss of the ability to call for emergency aid will have an obvious effect of postponing appropriate medical care to many individuals. Additionally, the isolation that stems from a lack of communication and information transfer can also have psychological effects as family groups find themselves without direction or reassurance from authorities.