Epidemiologic and virologic assessment of the 2009 influenza A (H1N1) pandemic on selected temperate countries in the Southern Hemisphere: Argentina, Australia, Chile, New Zealand and South Africa

• Published in: Influenza and other respiratory viruses 2011-11, Vol.5 (6), p.e487-e498
• Main Authors: Van Kerkhove, Maria D., Mounts, Anthony W., Mall, Sabine, Vandemaele, Katelijn A.H., Chamberland, Mary, dos Santos, Thais, Fitzner, Julia, Widdowson, Marc‐Alain, Michalove, Jennifer, Bresee, Joseph, Olsen, Sonja J., Quick, Linda, Baumeister, Elsa, Carlino, Luis O., Savy, Vilma, Uez, Osvaldo, Owen, Rhonda, Ghani, Fatima, Paterson, Bev, Forde, Andrea, Fasce, Rodrigo, Torres, Graciela, Andrade, Winston, Bustos, Patricia, Mora, Judith, Gonzalez, Claudia, Olea, Andrea, Sotomayor, Viviana, Najera De Ferrari, Manuel, Burgos, Alejandra, Hunt, Darren, Huang, Q. Sue, Jennings, Lance C., Macfarlane, Malcolm, Lopez, Liza D., McArthur, Colin, Cohen, Cheryl, Archer, Brett, Blumberg, Lucille, Cengimbo, Ayanda, Makunga, Chuma, McAnerney, Jo, Msimang, Veerle, Naidoo, Dhamari, Puren, Adrian, Schoub, Barry, Thomas, Juno, Venter, Marietjie
• Format: Article
• Language: English
• Subjects: Australasia - epidemiology; H1N1; Humans; Influenza A Virus, H1N1 Subtype - genetics; Influenza A Virus, H1N1 Subtype - isolation & purification; Influenza A Virus, H1N1 Subtype - physiology; influenza circulation; Influenza, Human - epidemiology; Influenza, Human - transmission; Influenza, Human - virology; Original; pandemic; Pandemics; Population Surveillance; severity; South Africa - epidemiology; South America - epidemiology; Southern Hemisphere; transmission
• ISSN: 1750-2640; 1750-2659
• DOI: 10.1111/j.1750-2659.2011.00249.x

Please cite this paper as: Van Kerkhove et al. (2011) Epidemiologic and virologic assessment of the 2009 influenza A (H1N1) pandemic on selected temperate countries in the Southern Hemisphere: Argentina, Australia, Chile, New Zealand and South Africa. Influenza and Other Respiratory Viruses 5(6), e487–e498. Introduction and Setting  Our analysis compares the most comprehensive epidemiologic and virologic surveillance data compiled to date for laboratory‐confirmed H1N1pdm patients between 1 April 2009 ‐ 31 January 2010 from five temperate countries in the Southern Hemisphere–Argentina, Australia, Chile, New Zealand, and South Africa. Objective  We evaluate transmission dynamics, indicators of severity, and describe the co‐circulation of H1N1pdm with seasonal influenza viruses. Results  In the five countries, H1N1pdm became the predominant influenza strain within weeks of initial detection. South Africa was unique, first experiencing a seasonal H3N2 wave, followed by a distinct H1N1pdm wave. Compared with the 2007 and 2008 influenza seasons, the peak of influenza‐like illness (ILI) activity in four of the five countries was 3‐6 times higher with peak ILI consultation rates ranging from 35/1,000 consultations/week in Australia to 275/100,000 population/week in New Zealand. Transmission was similar in all countries with the reproductive rate ranging from 1.2–1.6. The median age of patients in all countries increased with increasing severity of disease, 4–14% of all hospitalized cases required critical care, and 26–68% of fatal patients were reported to have ≥1 chronic medical condition. Compared with seasonal influenza, there was a notable downward shift in age among severe cases with the highest population‐based hospitalization rates among children