Objective: Influenza is an infectious respiratory disease that causes widespread epidemics and pandemics in the community. It is usually self-limiting but may cause significant morbidity and mortality due to complications. We aimed at evaluating the clinical, laboratory and prognosis of adult patients hospitalised with a pre-diagnosis of seasonal influenza.Materials and methods: It is a descriptive study based on the data from 50 patients hospitalised with a preliminary diagnosis of seasonal influenza between 1 December 2015 and 31 January 2016.Results: The average age of the patients was 55.44±17.17 years (20-89) and 64% of them were women. Of the cases, 36% were H1N1 positive, 30% were H3N2 positive and 34% had negative PCR results. The time from the onset of symptoms to hospital admission was 3.72±2.51 days (1-11). Comorbidities were present in 38 (76%) patients. Four patients had mortality.Conclusion: Influenza can be self-limited according to the characteristics of the host, as well as cause mortality. In this study, it was found to cause severe illness and death in a healthy young adult. Therefore, it is important to avoid contact with infected patients, hand washing and vaccination to reduce influenza and its complications. In addition, if our preliminary diagnosis of influenza continues, further evaluations should be made even if the PCR is negative.