A higher-than-normal body temperature is called "Fever or pyrexia" Fever usually occurs in response to an infection as with the flu virus or inflammation that occurs with tissue injury or disease.almost any infection can cause a fever. some infections are..

Infections: pneumonia,bone,skin,cellulite,meningitis, tuberculosis,colds,flu,ear infection,sinus infections,urinary tract infection,bacterial gastroenteritis...

what to eat during Fever?? In a fever time eat fruits,drink vegetable juices,chicken soup and herbal tea.Drink plenty of clean water and avoid drink milk and eat milk products.Avoid eating red meat, fish,shellfish and organ meats because are not easy to digest.
Drinks like bottled water,carbonated soft drinks and beverages such as coffee and tea should be avoided.
Eat cooked food.and eat rice porridge with ginger made with vegetable broth. this food is easy to digest and has healing properties.Alcohol,tobacco and smoke should be avoided.Cooked Chicken, fish and bananas support the health of the organs by generating infection fighting white blood cells.