Background: Influenza is a contagious and acute viral disease caused by influenza viruses involving upper and lower respiratory tract system, especially in the cold seasons. Children aged less than 5 years old, elderly people, immunocompromised patients, pregnant women, and people with certain health conditions are at a higher risk for the disease and severe complications. Objectives: Due to the serious complications of influenza in certain groups, it is important to know which group of people are more at risk and need prevention strategies. This study aimed to investigate the patients with confirmed influenza, identify the people who are at a higher risk for infection, and assess the clinical outcomes of disease among patients. Methods: In this cross-sectional and descriptive study, we studied the files of all patients with confirmed influenza referred to the health centers in Mashhad, Iran, during autumn and winter of 2019 when influenza virus was prevalent. The disease was confirmed by reverse transcription polymerase chain reaction (RT-PCR) method. We studied all registered data related to the flu, including gender, age, residency, history of vaccination, risk factors, complications, and clinical outcomes. Results: In this study, 2977 patients (3% outpatients vs. 97% hospitalized) with flu like syndrome were tested by RT-PCR for influenza. Out of 84 outpatients, only two cases were positive for influenza. Among hospitalized patients, 80 cases (51% male vs. 49% female; age range: 1 - 87 years) had a positive RT-PCR test, and influenza type A was seen in 95% of cases. Pneumonia was the most common complication. Death happened in 29 (35.36%) patients and three (33.33%) cases with risk factors. The highest number of influenza patients (31 [37.8%]) had been reported from district No. 3 of Mashhad municipality, which is a crowded place and near the holy shrine. Conclusions: The results showed a high prevalence of complication and death among hospitalized patients, especially among those who did not have a risk factor for influenza viruses. Comprehensive vaccination programs and promotion of knowledge about transmission routes are two important measures for disease prevention and lower death rates.