To elucidate the prognostic factors for fatal adult influenza pneumonia.

Complicated influenza pneumonia is a notifiable disease in Taiwan. In this retrospective nationwide cohort, medical records were reviewed in 38 qualifying cases from 2001 to 2007. In-hospital mortality was the primary endpoint of this study.

The median patient age was 52 years, with the in-hospital mortality rate of 44.7%. Influenza A virus was found in 25 patients and influenza B was in 13 patients. Fifty percent of patients had no comorbidities. More than half of the patients developed sepsis, septic shock, respiratory failure or acute respiratory distress syndrome. The median duration from symptom onset to hospital visit was 3 days, and from hospital visit to death was 4 days. A univariate analysis demonstrated poor prognosis in patients with shock, respiratory rate ≥25/min, arterial pH<7.35, creatinine≥2mg/dL and Pneumonia Severity Index IV or V. A multivariate analysis showed an association with mortality in patients with APACHE II score ≥20 (hazard ratio 5.941, p=0.024) or PaO₂/FiO₂ ratio <150 (hazard ratio 4.194, p=0.017).

Clinical knowledge of identified prognostic factors for mortality may aid management of adult influenza pneumonia.