. Feverish child. Four-year-old feverish girl being given a spoonful of medicine by her mother. The mother is checking her daughter's temperature by placing a hand on her forehead. Fever, known as pyrexia, is defined as a body temperature above 37 Celsius (98.6 Fahrenheit), when the temperature is checked orally. Most fevers are caused by bacterial or viral infections and may be accompanied by other symptoms such as shivering, sweating, headaches, thirst and hot skin. MODEL RELEASED