Background:   Fever is the most common presenting problem during the monsoon and post monsoon season in most parts of south india. Despite dramatic advances in hygiene, immunisation and antimicrobial therapy, infectious diseases are still responsible for a major global health burden.

Objective: To  study  the  etiological and clinical profile of acute febrile illness in adult patients admitted to Medicine ACSR Govt Medical College,Nellore during the months of September and October 2017.

Materials and Methods: This   observational study was conducted in ACSR Government Medical College, Nellore. All adult patients presenting with acute fever of 3–14 days duration were evaluated for etiology,  clinical presentation and outcome were analyzed. Results: The study   included 378 patients. A microbiological cause could not be identified in 78.03% of our patients.   Followed by dengue (7.6%), malaria (3.4%), enteric fever (3.17%),upper respiratory tract infections in (7.4%).Though  fever with thrombocytopenia was present in (57.93%) Dengue was not the etiological factor and most of them were due to unidentified viral fevers. The mean time to presentation was longer in enteric fever (9.9 [4.7] days) . Bleeding manifestations were seen in (8.9%) total (n= 34) patients.     The overall mortality rate was (1.05%)n=4, and was highest with  Dengue hemorrhagic fever .  Outcome was good with (98.94%) n=374, discharged after complete recovery. Conclusion:  In a large number of patients with acute febrile illness, the exact cause could not be identified. As alarmed Dengue was not the common etiological factor in majority of patients with thrombocytopenia.