title: Hepatitis B virus transmission by blood transfusion during 4 years of individual-donation nucleic acid testing in South Africa: estimated and observed window period risk.
abstract: BACKGROUND
  Since October 2005, a total of 2,921,561 blood donations have been screened by the South African National Blood Service for hepatitis B virus (HBV) by individual-donation nucleic acid testing (ID-NAT). Over 4 years, 149 hepatitis B surface antigen-negative acute-phase HBV NAT-positive donations were identified (1:19,608). The lookback program identified one probable HBV transmission.
  
  
  METHODS
  The complete genomes of HBV isolated from the donor and recipient were sequenced, cloned, and analyzed phylogenetically. The HBV window period (WP) transmission risk was estimated assuming a minimum infectious dose of 3.7 HBV virions and an incidence rate correction factor of 1.34 for transient detectability of HBV DNA.
  
  
  RESULTS
  Of 149 acute-phase HBV NAT yields, 114 (1:25,627) were classified as pre-antibody to hepatitis B core antigen (anti-HBc) WP and 35 (1:83,473) as post-anti-HBc WP. The acute-phase transmission risk in the HBV DNA-negative pre- and post-anti-HBc WPs (of 15.3 and 1.3 days, respectively) was estimated at 1:40,000 and 1:480,000, respectively. One HBV transmission (1:2,900,000) was identified in a patient who received a transfusion from an ID-NAT-nonreactive donor in the pre-anti-HBc WP. Sequence analysis confirmed transmission of HBV Subgenotype A1 with 99.7% nucleotide homology between donor and recipient strains. The viral burden in the infectious red blood cell unit was estimated at 32 (22-43) HBV DNA copies/20 mL of plasma.
  
  
  CONCLUSIONS
  We report the first known case of transfusion-transmitted HBV infection by blood screened using ID-NAT giving an observed HBV transmission rate of 0.34 per million. The estimated pre-acute-phase transmission risk in the ID-NAT screened donor population was 73-fold higher than the observed WP transmission rate.
authors: Donation Testing Department, South African National Blood Service (SANBS), Roodepoort, South Africa. marion.vermeulen@sanbs.org.za
authors: Marion
authors: M
authors: Vermeulen
authors: Caroline
authors: C
authors: Dickens
authors: Nico
authors: N
authors: Lelie
authors: Evangelia
authors: E
authors: Walker
authors: Charl
authors: C
authors: Coleman
authors: Mark
authors: M
authors: Keyter
authors: Ravi
authors: R
authors: Reddy
authors: Robert
authors: R
authors: Crookes
authors: Anna
authors: A
authors: Kramvis
mesh_terms: D000208:Acute Disease; D004279:DNA, Viral / Q000097:blood*; D006509:Hepatitis B / Q000175:diagnosis / Q000635:transmission*; D006801:Humans; D010802:Phylogeny; D012306:Risk; D017422:Sequence Analysis, DNA; D065227:Transfusion Reaction; D019562:Viral Load
chemical_list: D004279:DNA, Viral