title: Introduction of 2009 pandemic influenza A virus subtype H1N1 into South Africa: clinical presentation, epidemiology, and transmissibility of the first 100 cases.
abstract: BACKGROUND
  We documented the introduction of 2009 pandemic influenza A virus subtype H1N1 (A[H1N1]pdm09) into South Africa and describe its clinical presentation, epidemiology, and transmissibility.
  
  
  METHODS
  We conducted a prospective descriptive study of the first 100 laboratory-confirmed cases of A(H1N1)pdm09 infections identified through active case finding and surveillance. Infected patients and the attending clinicians were interviewed, and close contacts were followed up to investigate household transmission.
  
  
  RESULTS
  The first case was confirmed on 14 June 2009, and by 15 July 2009, 100 cases were diagnosed. Forty-two percent of patients reported international travel within 7 days prior to onset of illness. Patients ranged in age from 4 to 70 years (median age, 21.5 years). Seventeen percent of household contacts developed influenza-like illness, and 10% of household contacts had laboratory-confirmed A(H1N1)pdm09 infection. We found a mean serial interval (± SD) of 2.3 ± 1.3 days (range, 1-5 days) between successive laboratory-confirmed cases in the transmission chain.
  
  
  CONCLUSIONS
  A(H1N1)pdm09 established itself rapidly in South Africa. Transmissibility of the virus was comparable to observations from outside of Africa and to seasonal influenza virus strains.
authors.affiliation: National Institute for Communicable Diseases, National Health Laboratory Service, University of Witwatersrand, Johannesburg, South Africa. bretta@nicd.ac.za
authors.forename: Brett N
authors.initials: BN
authors.lastname: Archer
authors.forename: Geraldine A
authors.initials: GA
authors.lastname: Timothy
authors.forename: Cheryl
authors.initials: C
authors.lastname: Cohen
authors.forename: Stefano
authors.initials: S
authors.lastname: Tempia
authors.forename: Mmampedi
authors.initials: M
authors.lastname: Huma
authors.forename: Lucille
authors.initials: L
authors.lastname: Blumberg
authors.forename: Dhamari
authors.initials: D
authors.lastname: Naidoo
authors.forename: Ayanda
authors.initials: A
authors.lastname: Cengimbo
authors.forename: Barry D
authors.initials: BD
authors.lastname: Schoub
mesh_terms: D000293:Adolescent; D000328:Adult; D017677:Age Distribution; D000368:Aged; D002648:Child; D002675:Child, Preschool; D005192:Family Health; D005260:Female; D006801:Humans; D053118:Influenza A Virus, H1N1 Subtype / Q000302:isolation & purification*; D007251:Influenza, Human / Q000453:epidemiology* / Q000473:pathology* / Q000635:transmission; D008297:Male; D008875:Middle Aged; D011446:Prospective Studies; D013019:South Africa / Q000453:epidemiology; D014195:Travel; D055815:Young Adult