Epidemiological characterization of influenza in Northern Mexico

Influenza viruses cause a potentially fatal, highly contagious respiratory disease. Influenza A virus subtypes H1N1 and H3N2, and both lineages of the influenza B virus have affected the Mexican population. The present study aimed to determine the epidemiological characteristics of influenza infections in Northern Mexico during five flu seasons and determines the risk factors for hospitalization. For this purpose, 3,482 patients with confirmed influenza infection tested at the Public Health State Laboratory of Nuevo León using reverse transcription‑quantitative PCR from October, 2009 to December, 2014 were evaluated. Patient demographics and clinical characteristics were determined, and data were collected and analyzed. Pandemic influenza A H1N1 subtype was responsible for 52% of the cases in the present study;the influenza A H3N2 subtype was responsible for 27% of cases and the influenza B virus for 12% of cases. In total, 75% of the patients (n=2,611) received ambulatory treatment and 25% (n=871) were hospitalized. The number of hospitalized patients varied across the different seasons analyzed. A greater number of comorbidities were observed in hospitalized patients than the ambulatory patients;64% of patients with chronic obstructive pulmonary disease (COPD), 60% of patients with chronic kidney disease, and 51% of patients with diabetes were hospitalized. Of the total number of vaccinated patients, only 18% were hospitalized, in contrast to 27% of unvaccinated patients. On the whole, the present study describes the influenza cases identified in the metropolitan area of Monterrey, Mexico. The median age and clinical characteristics of the patients varied according to the season with increasing age, and the presence of dyspnea, polypnea, cyanosis, malaise, COPD, diabetes, or no vaccination, were associated with an increased risk of hospi‑ talization. This clinical characterization becomes relevant as coronavirus 2019 spreads worldwide, rendering its differen‑ tial diagnosis necessary in respiratory diseases that usually lead to hospitalization, such as influenza. © 2021 Spandidos Publications. All Rights Reserved.