What is, and who is at risk for heat stroke?

Heat stroke is a form of hyperthermia, an abnormally elevated body temperature with accompanying physical symptoms including changes in the nervous system function. Unlike heat cramps and heat exhaustion, two other forms of hyperthermia that are less severe, heat stroke is a true medical emergency that is often fatal if not properly and promptly treated. Heat stroke is also sometimes referred to as heatstroke or sun stroke. Severe hyperthermia is defined as a body temperature of 104 F (40 C) or higher.
The body normally generates heat as a result of metabolism, and is usually able to dissipate the heat by radiation of heat through the skin or by evaporation of sweat. However, in extreme heat, high humidity, or vigorous physical exertion under the sun, the body may not be able to dissipate the heat and the body temperature rises, sometimes up to 106 F (41.1 C) or higher. Another cause of heat stroke is dehydration. A dehydrated person may not be able to sweat fast enough to dissipate heat, which causes the body temperature to rise.
Those most susceptible (at risk) individuals to heart strokes include:

• infants,
  
• the elderly (often with associated heart diseases, lung diseases, kidney diseases, or who are taking medications that make them vulnerable to dehydration and heat strokes),
  
• athletes, and
  
• individuals who work outside and physically exert themselves under the sun.