title: 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.
abstract: 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 <5 years old. National population-based mortality rates ranged from 0.8-1.5/100,000.
  
  
  CONCLUSIONS
  The difficulty experienced in tracking the progress of the pandemic globally, estimating its severity early on, and comparing information across countries argues for improved routine surveillance and standardization of investigative approaches and data reporting methods.
authors.affiliation: World Health Organization, Imperial College London, UK. m.vankerkhove@imperial.ac.uk
authors.forename: Maria D
authors.initials: MD
authors.lastname: Van Kerkhove
authors.forename: Anthony W
authors.initials: AW
authors.lastname: Mounts
authors.forename: Sabine
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authors.lastname: Mall
authors.forename: Katelijn A H
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authors.lastname: Baumeister
authors.forename: Luis O
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authors.lastname: Carlino
authors.forename: Vilma
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authors.forename: Fatima
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authors.forename: Bev
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authors.forename: Andrea
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authors.forename: Rodrigo
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authors.lastname: Fasce
authors.forename: Graciela
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authors.lastname: Torres
authors.forename: Winston
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authors.lastname: Andrade
authors.forename: Patricia
authors.initials: P
authors.lastname: Bustos
authors.forename: Judith
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authors.lastname: Mora
authors.forename: Claudia
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authors.lastname: Gonzalez
authors.forename: Andrea
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authors.lastname: Olea
authors.forename: Viviana
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authors.lastname: Sotomayor
authors.forename: Manuel
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authors.lastname: Najera De Ferrari
authors.forename: Alejandra
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authors.lastname: Burgos
authors.forename: Darren
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authors.lastname: Hunt
authors.forename: Q Sue
authors.initials: QS
authors.lastname: Huang
authors.forename: Lance C
authors.initials: LC
authors.lastname: Jennings
authors.forename: Malcolm
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authors.lastname: Macfarlane
authors.forename: Liza D
authors.initials: LD
authors.lastname: Lopez
authors.forename: Colin
authors.initials: C
authors.lastname: McArthur
authors.forename: Cheryl
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authors.lastname: Cohen
authors.forename: Brett
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authors.lastname: Archer
authors.forename: Lucille
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authors.lastname: Blumberg
authors.forename: Ayanda
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authors.lastname: Cengimbo
authors.forename: Chuma
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authors.lastname: Makunga
authors.forename: Jo
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authors.lastname: McAnerney
authors.forename: Veerle
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authors.lastname: Msimang
authors.forename: Dhamari
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authors.lastname: Naidoo
authors.forename: Adrian
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authors.lastname: Puren
authors.forename: Barry
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authors.lastname: Schoub
authors.forename: Juno
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authors.forename: Marietjie
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mesh_terms: D044362:Australasia / Q000453:epidemiology; D006801:Humans; D053118:Influenza A Virus, H1N1 Subtype / Q000235:genetics / Q000302:isolation & purification / Q000502:physiology*; D007251:Influenza, Human / Q000453:epidemiology* / Q000635:transmission / Q000821:virology*; D058873:Pandemics; D011159:Population Surveillance; D013019:South Africa / Q000453:epidemiology; D013020:South America / Q000453:epidemiology