The acute undifferentiated febrile illness (AUFIs) are common clinical problem in south Asia. AUFIs represent a considerable burden of disease with diagnostic and therapeutic challenges. Empirical broad-spectrum antimicrobials are generally prescribed but with little evidence-based guidance on likely etiologies or potential treatment responses. A variety of etiologies have been reportedin patients presenting with acute undifferentiated fever in tropical areas. malaria, dengue fever, scrub typhus, other rickettsioses, leptospirosis, and enteric fever are common cause of acute undifferentiated fever, causing considerable morbidity, mortality, and economic burden. However the etologic spectrum of acute undifferentiated fever has been poorly characterized in developing and under developing nation in tropical areas because of limited diagnostic capacity.