It is the most common killer of walkers in wilderness areas. Early signs of hypothermia are persistent shivering, frequent stumbling and exhaustion. Get the victim out of the wind and rain and into dry clothes. Give warm sugary drinks and place them in a dry sleeping bag. In advanced cases, shivering stops, the patient becomes irrational and, if untreated, will lapse into coma.
Death soon follows.
Treatment is the same as for milder cases but have someone get into the sleeping bag with the person to transfer body heat via skin to skin contact. If breathing stops give mouth to mouth resuscitation. Aim to slowly and gently re-warm the victim. Even if the patient appears to have recovered it is necessary to treat them as a stretcher case. Get medical assistance to the patient as soon as possible.