Fever may be caused by multiple reasons including infections, cancer, autoimmune, inflammatory conditions etc.
Fever of unknown origin (Pyrexia of Unknown Origin i.e, PUO) is when no cause of fever is found inspite of basic/advanced investigations. Any of the above may be responsible for this. Typically in western countries, compared with other regions of the world, infections are less frequent, and inflammatory causes more common. In low and middle-income countries, including India, enteric fever (typhoid fever), brucellosis, tuberculosis, endocarditis, and intra-abdominal abscesses are the most commonly reported infectious causes of FUO.
It is crucial to see an infectious diseases specialist in cases where cause of fever is not being identified. The evaluation needs a very detailed history and examination skills and infectious diseases specialist is best suited for the job. Patients who are frequent travellers especially are at increased risk, because they are exposed to various ecological niches. Additionally it is important to choose the right investigation modality, avoid unnecessary higher antibiotics before identifying the exact cause. The prognosis of any case depends on early diagnosis and treatment. Hence patients must seek early consultation from infection specialists who are well equipped to analyse and mange such cases.