title: Comparison of pandemic (H1N1) 2009 and seasonal influenza, Western Australia, 2009.
abstract: We compared confirmed pandemic (H1N1) 2009 influenza and seasonal influenza diagnosed in Western Australia during the 2009 influenza season. From 3,178 eligible reports, 984 pandemic and 356 seasonal influenza patients were selected; 871 (88.5%) and 288 (80.9%) were interviewed, respectively. Patients in both groups reported a median of 6 of 11 symptoms; the difference between groups in the proportion reporting any given symptom was < or =10%. Fewer than half the patients in both groups had > or =1 underlying condition, and only diabetes was associated with pandemic (H1N1) 2009 influenza (odds ratio [OR] 1.9, 95% confidence interval [CI] 1.1-3.5). A total of 129 (14.8%) persons with pandemic (H1N1) 2009 and 36 (12.5%) persons with seasonal influenza were hospitalized (p = 0.22). After controlling for age, we found that patient hospitalization was associated with pandemic (H1N1) 2009 influenza (OR 1.5; 95% CI 1.1-2.1). Contemporaneous pandemic and seasonal influenza infections were substantially similar in terms of patients' symptoms, risk factors, and proportion hospitalized.
authors.affiliation: Communicable Disease Control Directorate, Perth, Western Australia, Australia.
authors.forename: Dale
authors.initials: D
authors.lastname: Carcione
authors.forename: Carolien
authors.initials: C
authors.lastname: Giele
authors.forename: Gary K
authors.initials: GK
authors.lastname: Dowse
authors.forename: Donna B
authors.initials: DB
authors.lastname: Mak
authors.forename: Leigh
authors.initials: L
authors.lastname: Goggin
authors.forename: Kelly
authors.initials: K
authors.lastname: Kwan
authors.forename: Simon
authors.initials: S
authors.lastname: Williams
authors.forename: David
authors.initials: D
authors.lastname: Smith
authors.forename: Paul
authors.initials: P
authors.lastname: Effler
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D002648:Child; D002675:Child, Preschool; D048909:Diabetes Complications / Q000453:epidemiology; D005260:Female; D006801:Humans; D007223:Infant; D007231:Infant, Newborn; D053118:Influenza A Virus, H1N1 Subtype; D007251:Influenza, Human / Q000150:complications / Q000453:epidemiology*; D008297:Male; D008875:Middle Aged; D058873:Pandemics; D012307:Risk Factors; D012621:Seasons; D014904:Western Australia / Q000453:epidemiology; D055815:Young Adult