Impact and characteristics of hospital-acquired influenza over 10 seasons in a third-level university hospital

Abstract

Objectives: To analyze the characteristics of patients with nosocomial flu, to compare them with patients with community-acquired influenza to study possible differences and to identify possible risk factors associated with this type of flu.

Patients and methods: Observational, cross-sectional and retrospective study of hospitalized patients with a microbiological confirmation of influenza in a third-level university hospital over 10 seasons, from 2009 to 2019. Nosocomial influenza was defined as that infection whose symptoms began 72h after hospital admission, and its incidence, characteristics and consequences were further analyzed.

Results: A total of 1260 hospitalized patients with a microbiological diagnosis of influenza were included, which 110 (8.7%) were nosocomial. Patients with hospital-acquired influenza were younger (71.74±16.03 years, P=0.044), had a longer hospital stay (24.25±20.25 days, P<0.001), had more frequently a history of chronic pulmonary pathologies (P=0.010), immunodeficiency (P<0.001), and were associated with greater development of bacterial superinfection (P<0.001), respiratory distress (P=0.003), and admission to the intensive care unit (ICU) (P<0.001). In the multivariate logistic regression analysis, the following characteristics were identified as independent risk factors: immunodeficiency (ORa=2.33; 95% CI: 1.47-3.60); ICU admission (ORa=4.29; 95% CI: 2.23-10.91); bacterial superinfection (ORa=1.64; 95% CI: 1.06-2.53) and respiratory distress (ORa=3.88; 95% CI: 1.23-12.23).

Conclusions: Nosocomial influenza is more common in patients with a history of immunodeficiency. In addition, patients with hospital-acquired influenza had an increased risk of bacterial superinfection, admission to the ICU, and development of respiratory distress.

Keywords: Flu; Gripe; Hospital; Immunodeficiency; Influenza; Inmunodeficiencia; Nosocomial; Virus.