Between October 2013 and April 2014, the Centers for Disease Control and Prevention reported a high incidence of AH1N1 influenza cases. Not all suspicious cases of influenza are confirmed; however, all patients need treatment and generate additional costs to the institutions. Our objective was to describe the characteristics of the patients treated for influenza suspicion at Hospital de Especialidades in Centro Médico Nacional Siglo XXI during a new epidemic. Cross-sectional study of all cases admitted at the Emergency Service (of the aforementioned hospital) for influenza-like illness, defined according to current guidelines. Based on these guidelines, we analyzed the risk factors that may have increased the severity of the infection. We registered a total of 109 patients with a mean age of 44 years, 78 % were under 60 years of age, 62 % were women, 75 % had at least one comorbidity, such as obesity (26 %) or hypertension (27 %). Only 65 patients had results from a confirmatory test, 33.8 % had positive diagnosis, and 21 % of them eventually died. The frequency of confirmed cases for influenza infection is low. The risk factors associated with complications and increased mortality are hypertension, leukocytosis and clinical presentation of severe acute respiratory syndrome.