Patient characteristics and outcomes of hospitalization for influenza infection in Hong Kong

Objectives: Hospitalized influenza cases add burden to the public healthcare system of Hong Kong, especially during influenza peak seasons. In winter peak seasons of 2015 and 2016, the medical in-patient bed occupancy rates of acute hospitals exceeded 100%. We aimed to describe the patient characteristics, clinical and economic outcomes of hospitalized influenza infection treatment. Methods: A retrospective, observational study was conducted in hospitalized adult patients with laboratory-confirmed influenza infection in a Hong Kong teaching hospital from October 2014 to September 2015. Patient demographics and treatment outcomes (including influenza-related length of hospital stay (LOS) and cost of treatment) were collected. Data were presented by descriptive statistics. Results: There were 1,127 laboratory-confirmed adult influenza cases during the study period, and 116 cases (with 57 (49.1%) male) were randomly selected and reviewed. Mean age was 75±18 years and 94 (81%) were ≥ 65 years. Eight-nine (76.7%) cases were community-acquired. There were 89 (83.6%) patients with major underlying chronic comorbidities and 49 (42.2%) presented respiratory complications. Influenza type A accounted for 103 (88.8%) cases and 13 (11.2%) were influenza type B. Antiviral therapy was initiated within 2 days, 5 days and 7 days from symptom onset in 61 (52.6%), 107 (92.2%) and 113 (97.4%) patients, respectively. There were 2 (1.7%) patients admitted to ICU and 3 (2.6%) cases of influenza-related death. The median LOS was 5 days (IQR 3-7 days), and the median treatment cost was HKD38,719 (IQR HKD30,300-52,569) (USD1= HKD7.8). Conclusions: Hospitalization for influenza in Hong Kong occurred mostly in elderly with underlying chronic diseases from community setting and economic burden was substantial.