title: The 2003 West Nile virus United States epidemic: the America's Blood Centers experience.
abstract: BACKGROUND
  A detailed assessment of West Nile virus (WNV) yield is needed to evaluate the effectiveness of the WNV nucleic acid amplification technology (NAT) screening implemented in 2003.
  
  
  METHODS
  WNV NAT screening and donation data were compiled from members of America's Blood Centers, which collect nearly 50 percent of the US blood supply. WNV RNA screening was performed with either the Gen-Probe/Chiron Procleix transcription-mediated amplification assay or the Roche TaqScreen polymerase chain reaction. Results of alternate NAT and WNV immunoglobulin M (IgM) antibody assays conducted on index and follow-up samples were obtained from test manufacturers. Presumed WNV positivity was based on NAT repeat reactivity of the individual index donation whereas confirmatory status was based on additional IgM testing of the index donation and NAT and serology testing of follow-up samples.
  
  
  RESULTS
  From July through October 2003, 2.5 million donations were screened for WNV RNA. Of 877 NAT-reactive donations (screening positivity rate of 3.5 per 10,000 units), 430 (49%) were confirmed positive, whereas 68 (8%) lacking follow-up data remained presumed positive. The sensitivity and positive predictive value of a presumed viremic result relative to final confirmatory status were 92 and 99 percent, respectively. WNV activity was highest in the central plains with prevalence per 10,000 peaking August 1 to 15 in Colorado (67.7) and South Dakota (77.5) and August 16 to 31 in Wyoming (74.1) and North Dakota (102.0).
  
  
  CONCLUSIONS
  WNV screening interdicted many viremic units, thereby reducing transfusion-transmitted infections. This study demonstrates that a national collaborative effort facilitates timely surveillance of blood donor infectious disease prevalence rates.
authors.affiliation: Westat, Rockville, Maryland, USA.
authors.forename: Steven
authors.initials: S
authors.lastname: Kleinman
authors.forename: Simone A
authors.initials: SA
authors.lastname: Glynn
authors.forename: Michael
authors.initials: M
authors.lastname: Busch
authors.forename: Deborah
authors.initials: D
authors.lastname: Todd
authors.forename: Laurie
authors.initials: L
authors.lastname: Powell
authors.forename: Larry
authors.initials: L
authors.lastname: Pietrelli
authors.forename: George
authors.initials: G
authors.lastname: Nemo
authors.forename: George
authors.initials: G
authors.lastname: Schreiber
authors.forename: Celso
authors.initials: C
authors.lastname: Bianco
authors.forename: Louis
authors.initials: L
authors.lastname: Katz
mesh_terms: D001771:Blood Banks / Q000706:statistics & numerical data*; D001782:Blood Donors; D004196:Disease Outbreaks / Q000706:statistics & numerical data*; D006801:Humans; D008403:Mass Screening; D015995:Prevalence; D012367:RNA, Viral / Q000032:analysis; D012621:Seasons; D014481:United States / Q000453:epidemiology; D014901:West Nile Fever / Q000097:blood* / Q000175:diagnosis / Q000453:epidemiology*; D014902:West Nile virus / Q000235:genetics / Q000302:isolation & purification*
chemical_list: D012367:RNA, Viral