title: Epidemiological and virological characterization of 2009 pandemic influenza A virus subtype H1N1 in Madagascar.
abstract: BACKGROUND
  Madagascar was one of the first African countries to be affected by the 2009 pandemic of influenza A virus subtype H1N1 [A(H1N1)pdm2009] infection. The outbreak started in the capital city, Antananarivo, and then spread throughout the country from October 2009 through February 2010.
  
  
  METHODS
  Specimens from patients presenting with influenza-like illness were collected and shipped to the National Influenza Center in Madagascar for analyses, together with forms containing patient demographic and clinical information.
  
  
  RESULTS
  Of the 2303 specimens tested, 1016 (44.1%) and 131 (5.7%) yielded A(H1N1)pdm09 and seasonal influenza virus, respectively. Most specimens (42.0%) received were collected from patients <10 years old. Patients <20 years old were more likely than patients >50 years old to be infected with A(H1N1)pdm09 (odds ratio, 2.1; 95% confidence interval, 1.7-2.6; P < .01). Although phylogenetic analyses of A(H1N1)pdm09 suggested multiple introductions of the virus into Madagascar, no antigenic differences between A(H1N1)pdm09 viruses recovered in Madagascar and those that circulated worldwide were observed.
  
  
  CONCLUSIONS
  The high proportion of respiratory specimens positive for A(H1N1)pdm09 is consistent with a widespread transmission of the pandemic in Madagascar. The age distribution of cases of A(H1N1)pdm09 infection suggests that children and young adults could be targeted for interventions that aim to reduce transmission during an influenza pandemic.
authors.affiliation: National Influenza Center, Virology Unit, Institut Pasteur de Madagascar, Université d’Ankatso, Antananarivo, Madagascar. jmheraud@pasteur.mg
authors.forename: Arnaud
authors.initials: A
authors.lastname: Orelle
authors.forename: Norosoa Harline
authors.initials: NH
authors.lastname: Razanajatovo
authors.forename: Soatiana
authors.initials: S
authors.lastname: Rajatonirina
authors.forename: Jonathan
authors.initials: J
authors.lastname: Hoffmann
authors.forename: Laurence
authors.initials: L
authors.lastname: Randrianasolo
authors.forename: Girard Marcellin
authors.initials: GM
authors.lastname: Razafitrimo
authors.forename: Dhamari
authors.initials: D
authors.lastname: Naidoo
authors.forename: Vincent
authors.initials: V
authors.lastname: Richard
authors.forename: Jean-Michel
authors.initials: JM
authors.lastname: Heraud
mesh_terms: D000293:Adolescent; D000328:Adult; D017677:Age Distribution; D000368:Aged; D002648:Child; D002675:Child, Preschool; D005260:Female; D005838:Genotype; D006801:Humans; D007223:Infant; D053118:Influenza A Virus, H1N1 Subtype / Q000145:classification / Q000235:genetics* / Q000302:isolation & purification*; D007251:Influenza, Human / Q000453:epidemiology* / Q000821:virology*; D008270:Madagascar / Q000453:epidemiology; D008297:Male; D008875:Middle Aged; D017720:Molecular Epidemiology; D008969:Molecular Sequence Data; D058873:Pandemics; D010802:Phylogeny; D012367:RNA, Viral / Q000235:genetics; D017422:Sequence Analysis, DNA; D055815:Young Adult
chemical_list: D012367:RNA, Viral