Hi, Thank you for your query on Healthcare Magic, The common causes of prolonged fever are Malaria, viral fevers, typhoid fever, pneumonia, urinary tract infections and some collagen disorders. The detection is aided by doing appropriate investigations like CBP, malarial parasite,widal test, blood culture, CUE, urine culture and collagen profile. Depending on history, fever pattern and physical examination your doctor will plan the investigations to detect the source and the cause of infection and plan empirical and the definitive treatment. Hope i have answered your query.