Acute fever or acute febrile illness is one of the most common presenting complaints to the physicians in OPDs and in emergency care, in children and in adults alike. Fever itself is not a disease; it is both a symptom and a sign of disease. India, being a tropical country, acute fever has myriad causes. Most fevers are infectious in origin due to bacterial, viral or parasitic protozoan infections notable among which are dengue, typhoid fever, malaria, Chikungunya, scrub typhus and rickettsial infections, Japanese encephalitis, leptospirosis, respiratory tract infections, sexually transmitted infections. The cause usually depends on the disease endemicity and seasonality of infections.