Characteristics of influenza in elderly patients with and without diabetes, hospitalized for severe acute respiratory infection in a tertiary care hospital from Bucharest Romania - a three-year prospective epidemiological surveillance study.

Introduction: Patients with diabetes may be at a higher risk of developing complicated influenza. We report the characteristics of influenza in hospitalized elderly patients with and without diabetes, in three consecutive influenza seasons.

Methods: The study included patients admitted for severe acute respiratory infection (SARI) in the National Institute for Infectious Diseases "Prof. Dr. Matei Balș", Bucharest, during a three-year active epidemiological surveillance study (2015/16, 2016/17, 2017/18), in the I-MOVE+ hospital network.

Results: A total of 349 patients were tested by PCR over the duration of the study. The percentage of patients with diabetes was comparable throughout the seasons: 34.7%, 28.3% and 30.4% (p=0.587). Influenza A was the main viral type circulating in 2015/16 and 2016/17 (100% and 97.6%) in our study population, while in 2017/18, B viruses predominated (90.0%). Diabetics presented a higher median number of comorbidities (3 vs. 2) p<0.001, and two-fold higher odds of also associating obesity (OR=2.1, 95%CI:1.3-3.4, p=0.003), compared to those without diabetes. Diabetics also tested positive for influenza more often (p=0.296). Only 6 patients with diabetes (5.4%) from our study had been vaccinated against influenza, and most (n=4) of those who had been vaccinated tested negative for influenza.

Conclusions: Our study is the first to describe the circulation of influenza viral types in elderly diabetic patients hospitalized for SARI. The results reinforce the national and international recommendation to vaccinate against influenza all patients with diabetes.