Q: I am 30 years old. I had fever for a week with shivering at nights. I got my blood and urine checked and was told that typhoid and malaria were negative. I even checked for dengue fever, but the results were negative. My blood report was totally normal but my urine report showed pus cells: 5-6. Some say that the shivering is due to the increased amount of pus cells found. Is it true? I got admitted to a very good hospital in Chennai where I was treated for enteric fever. Now I am ok but I want to know the cause for my fever?

A:Fever can be caused by a variety of conditions both infectious and non-infectious. Fever or pyrexia of unknown origin (PUO) is defined as any febrile illness (temperature greater than 38oC) lasting 3 weeks or longer, without any obvious cause and failure to reach a diagnosis despite one week of inpatient investigation. The causes of PUO include infections, neoplasms, connective tissue disorders, granulomatous diseases and drug reactions. Infectious causes are responsible for nearly one third cases of PUO. The common causes of infections include bacterial infections such as enteric fever, urinary tract infection, septicaemia associated with pneumonia, infective endocarditis, etc., tuberculosis, brucellosis, rheumatic fever, relapsing fever, leptospirosis, typhus fever, Q fever, etc. This also includes parasitic infections such as malaria, amoebic liver abscess, kala-azar, filariasis, toxoplasmosis, etc; and viral infections such as infectious mononucleosis, cytomegalovirus infection, hepatitis A virus infection, hepatitis B virus infection, HIV infection, etc; and fungal infections. Non-infectious causes of PUO includes neoplasms such as Hodgkin’s lymphoma, non-Hodgkin’s lymphoma, leukaemia, hypernephroma, hepatoma, etc.; connective tissue disorders such as systemic lupus erythematosus (SLE), polyarteritis nodosa, etc and granulomatous diseases such as sarcoidosis and Crohn’s diseases. Therefore the exact cause of the fever can only be ascertained by the treating physicians depending on clinical signs and symptoms supported with adequate laboratory test results.