Abstract: Objective To investigate the cause and clinical characteristics of patients with fever of unknown origin (FUO), and to summarize the clinical experience of its diagnosis and treatment. Methods Clinical data of 433 cases with FUO from the department of infectious diseases, Ruijin Hospital, Shanghai Jiao Tong University School of Medicine was retrospectively analyzed. These cases were divided into group A (2012-2014) and group B (2015-2017) according to their admission date. Results Among the 433 patients, group A included 154 cases of infectious diseases (79.38%), 7 cases of connective tissue disease (3.61%), 8 cases of tumor diseases (4.12%), 7 cases of other diseases (3.61%), and 18 cases of unknown origin (9.28%). Group B included 192 cases of infectious diseases (80.33%), 17 cases of connective tissue disease (7.11%), 12 cases of tumor diseases (5.02%), 6 cases of other diseases (2.51%), and 12 cases of unknown origin (5.02%). Conclusion The main cause in FUO was infectious diseases, followed by connective tissue diseases and tumor diseases. Moreover, connective tissue diseases and tumor diseases had an increasing trend in the past 3 years.

Key words: Fever of unknown origin, Causes, Clinical experience of diagnosis and treatment