PURPOSE: To describe the clinical characteristics and outcomes of all patients hospitalized with H1N1 2009 influenza in a defined urban population during influenza season, and to analyse risk factors for severity and intensive care unit (ICU) admission.
METHODS: Retrospective medical record review was performed of all patients with laboratory-confirmed H1N1 influenza, hospitalized in Newcastle, Australia between June and September 2009. Descriptive statistical analysis of aggregated data and intergroup comparisons by regression analysis were performed to look for predictors of greater length of hospital stay and ICU admission.
RESULTS: There was a total of 106 patients. 95% of hospital admissions occurred during July and August 2009, the peak winter months in Southern hemisphere. 34% of patients were children under 18 years. Only 7% were older than 65 years. 12 patients (17% of adults) were pregnant. 85% patients had an underlying medical condition and 44% had at least two such conditions.19% had radiographic findings of pneumonia on admission. Antiviral therapy was initiated in 73 patients (69%) at a median of 3 days after onset of illness. 18 patients (17%) were admitted to an ICU, of whom 8 required mechanical ventilation for a median period of 10 days and two required non-invasive ventilation. Four (4%) patients died. No pregnant patient required admission to ICU or died. Median length of hospital stay was 4 days. Patients with underlying chronic obstructive pulmonary disease (COPD) (odds ratio, 13.6; P=0.015) and hypertension (odds ratio, 8.3; P=0.002) had greater length of hospital stay. Chest radiographic changes of pneumonia (odds ratio, 4.03; P=0.016) at presentation carried a significantly greater risk for ICU admission.
CONCLUSION: COPD and hypertension predict a higher risk of prolonged hospitalization. Chest radiographic abnormalities of pneumonia at presentation predict greater risk for ICU admission.
CLINICAL IMPLICATIONS: During influenza season, patients with chest radiographic abnormalities suggestive of pneumonia should be promptly evaluated and treated for H1N1 influenza as early anti-viral therapy may reduce the risk of ICU admission and death.
DISCLOSURE: Rajesh Thomas, No Financial Disclosure Information; No Product/Research Disclosure Information