Background and Objectives: The first pandemic of the 21 ^st century was caused in 2009 by influenza A(H1N1). An increase in the number of cases caused by influenza A(H1N1) pdm09 was observed in 2013. The aim was to describe the number of influenza cases observed during 2013 in a general hospital of Argentina. Materials and Methods: A prospective, observational cohort of adult patients with influenza was confirmed by reverse transcription-polymerase chain reaction. Results: We analyzed 428 patients between epidemiological weeks 21 and 31, resulting in 134 (31%) patients who were positive for influenza A. Of these patients, 78% were infected with H1N1 (2009), 17% with H3, and 5% with a subtype that could not be determined. The mean patients' age was 53 ± 18 years. Eighty-three percent of patients had not been vaccinated, and no differences between vaccinated and nonvaccinated patients were observed. Seventy-five percent of patients had underlying conditions. Twenty-eight patients were treated as outpatients, and 86 required admission to the general ward, and 20 to the Intensive Care Unit. A significant difference in patient's age was observed between individuals infected with influenza H1N1 and those infected with other non-H1N1 subtypes. The mortality rate was 11%. In the multivariable analysis, mechanical ventilation (odds ratio: 27.66; 95% confidence interval [CI]: 6.43-119; P < 0.001) and cancer (odds ratio: 6.81; 95% CI: 1.25-37.13; P = 0.02) were predictors of mortality. Conclusions: We report a new wave of influenza A(H1N1). Most patients had underlying conditions, and a significant number of patients had not been vaccinated. Mortality was high; the only predictors of mortality were cancer and the need for mechanical ventilation.