Clinical and epidemiological profile of patients with severe H1N1/09 pandemic influenza in Australia and New Zealand: an observational cohort study
Allen C Cheng,
Christine Jenkins,
Louis Irving,
Richard Wood-Baker,
Tom Kotsimbos,
Robert J Hancox,
Anna Reynolds,
Simon G A Brown,
Graham Simpson,
Simon D Bowler,
Mark Holmes,
Philip Thompson,
Grant Waterer,
Paul M Kelly
Affiliations
Allen C Cheng
Infection Prevention and Healthcare Epidemiology Unit, Department of Infectious Diseases, Alfred Health, Melbourne, Victoria, Australia
Christine Jenkins
The George Institute for Global Health, Newtown, New South Wales, Australia
Louis Irving
Department of Respiratory and Sleep Medicine, The Royal Melbourne Hospital, Melbourne, Victoria, Australia
Richard Wood-Baker
4 NHMRC Centre of Research Excellence for Chronic Respiratory Disease, University of Tasmania, Hobart, Tasmania, Australia
Tom Kotsimbos
Department of Medicine, Monash University, Melbourne, Victoria, Australia
Robert J Hancox
1 Department of Preventive & Social Medicine, University of Otago, Dunedin, New Zealand
Anna Reynolds
2 Renal, Wirral University Teaching Hospital NHS Foundation Trust, Wirral, UK
Simon G A Brown
Department of Emergency Medicine, Royal Perth Hospital, University of Western Australia, and Centre for Clinical Research in Emergency Medicine, Western Australian Institute for Medical Research, Perth, Western Australia, Australia
Graham Simpson
Thoracic Medicine Department, Cairns Base Hospital, Cairns, Queensland, Australia
Simon D Bowler
Department of Respiratory Medicine, Mater Adult Hospital, South Brisbane, Queensland, Australia
Mark Holmes
The University of Adelaide, Adelaide, South Australia, Australia
Philip Thompson
Lung Institute of Western Australia and the Centre for Asthma, Allergy and Respiratory Research, University of Western Australia, Perth, Australia
Grant Waterer
Royal Perth Hospital, Perth, Western Australia, Australia
Paul M Kelly
National Centre for Epidemiology & Population Health, College of Medicine, Biology & Environment, Australian National University, Canberra, Australian Capital Territory, Australia
Background Pandemic influenza H1N1/09 emerged in April 2009 and spread widely in Australia and New Zealand. Although an unprecedented number of cases required intensive care, comparative community-based studies with seasonal influenza strains have not shown any significant differences in clinical symptoms or severity.Methods The authors performed active surveillance on confirmed influenza-related admissions and compared the clinical profile of patients with pandemic H1N1/09 influenza and patients with seasonal influenza at eight hospitals in Australia and one hospital in New Zealand.Results During the 1 July and 30 November 2009, 560 patients with confirmed influenza were admitted, of which 478 had H1N1/09, and 82 had other seasonal strains. Patients with H1N1/09 influenza were younger, were more likely to have fever and were more likely to be pregnant but less likely to have chronic obstructive pulmonary disease and ischaemic heart disease than patients with seasonal strains. Other clinical features and comorbidities were reported in similar proportions. Admission to intensive care was required in 22% of patients with H1N1/09 influenza and 12% in patients with other strains. Hospital mortality was 5% in patients with H1N1 influenza.Conclusions The clinical features of H1N1/09 influenza and seasonal strains were similar in hospitalised patients. A higher proportion of patients had comorbidities than had been reported in community-based studies. Although the overall mortality was similar, the authors found evidence that H1N1/09 caused severe disease in a higher proportion of hospitalised patients.
