Fever of Unknown Origin is defined as a fever above 38.3°C (101°F) that persists for more than three weeks and remains undiagnosed after an initial hospital investigation. FUO is not simply a prolonged fever — it is a specific clinical entity requiring methodical, expert investigation. The causes broadly fall into four categories: infectious diseases (tuberculosis, endocarditis, abscesses, typhoid, HIV), malignancies (lymphoma, leukaemia, solid tumours), autoimmune and inflammatory conditions (adult-onset Still's disease, vasculitis, SLE, rheumatoid arthritis), and miscellaneous causes (drug fever, factitious fever, inflammatory bowel disease). In India, infectious causes — particularly tuberculosis — account for a significant proportion of FUO cases, making clinical experience in an Indian setting particularly valuable. Dr. Atul Kakar's dual expertise in infectious disease and rheumatology gives him a uniquely broad perspective for FUO investigations, covering both the infectious and inflammatory/autoimmune causes that together account for the majority of cases.
About Fever of Unknown Origin
When should you seek care?
How Dr. Kakar approaches treatment.
Dr. Kakar follows a structured FUO workup: a detailed history (travel, exposures, animal contact, medications, family history), thorough clinical examination at each visit, and a tiered investigation strategy. First-line tests include full blood count, inflammatory markers (CRP, ESR, ferritin), blood cultures, tuberculosis testing (Mantoux, IGRA, sputum), chest X-ray, urine culture, and serology for common infections. Second-line investigations include CT chest/abdomen/pelvis, echocardiography, bone marrow biopsy, PET-CT for occult malignancy or vasculitis, and autoimmune panels (ANA, ANCA, RF). The cause is identified in approximately 70–80% of cases with a systematic approach. Treatment is directed at the confirmed underlying diagnosis.
When to see a specialist.
Seek specialist evaluation if you have had a fever above 38.3°C for more than 2–3 weeks, if standard antibiotics have not resolved a fever, if you have weight loss or night sweats alongside fever, or if initial investigations by a GP have not yielded a diagnosis. Early specialist review prevents unnecessary empirical antibiotic use and guides efficient, targeted investigation.