Outcomes and Prognostic Features of Patients With Influenza Requiring Hospitalization and Receiving Early Antiviral Therapy A Prospective Multicenter Cohort Study

BACKGROUND: In Japan, the routine use of early antiviral therapy for patients with influenza is standard. METHODS: This multicenter prospective cohort evaluation of hospitalized patients with laboratory-confirmed influenza identified prognostic factors among the patients receiving antiviral therapy. RESULTS: Of 1,345 patients with influenza (766 pediatric, 579 adult), excluding those aged < 1 year (who are not approved for antiviral therapy), 97.7% (1,224 of 1,253) received antiviral therapy. Among the adult patients, 24 (4.1%) died within 30 days, whereas none of the pediatric patients died. Five hundred twenty-eight (91.2%) adult patients had influenza A, 509 (87.9%) had a chronic underlying illness, and 211 (36.4%) had radiographically confirmed pneumonia. Twenty of the 24 patients who died had pneumonia of the following etiologies: Streptococcus pneumoniae (12.3%); Staphylococcus aureus (10.9%), including methicillin-resistant S aureus (MRSA) 3.3%; Enterobacteriaceae (8.1%); and Pseudomonas aeruginosa (3.3%). Of the adult patients, 151 were classified as having community-acquired pneumonia (CAP) and 60 as having health-care-associated pneumonia (HCAP). Inappropriate therapy was more common in HCAP than in CAP (15.2% vs 2%, P = .001). Potential multidrug-resistant (MDR) pathogens were more common (21.7% vs 2.6%, P < .001) in patients with HCAP, particularly MRSA (10% vs 0.7%, P = .002) and P aeruginosa (8.3% vs 1.3%, P = .021). Using Cox proportional hazards modeling with prescribed independent variables, male sex, severity score, serum albumin levels (malnutrition), and pneumonia were associated with survival 30 days from the onset of influenza. CONCLUSIONS: Among the prognostic factors, malnutrition and pneumonia are amenable to medical intervention. An opportunity exists to improve empirical therapy for patients with HCAP and influenza.