Transfusion-associated transmission of West Nile virus, United States 2003 through 2005.
BACKGROUND
National blood donation screening for West Nile virus (WNV) started in June 2003, after the documentation of WNV transfusion-associated transmission (TAT) in 2002.


METHODS
Blood donations were screened with investigational nucleic acid amplification assays in minipool formats. Blood collection agencies (BCAs) reported screening results to state and local public health authorities. Donor test results and demographic information were forwarded to CDC via ArboNET, the national electronic arbovirus surveillance system. State health departments and BCAs also reported suspect WNV TATs to CDC, which investigated these reports to confirm WNV infection in blood transfusion recipients in the absence of likely mosquito exposure.


RESULTS
During 2003 to 2005, a total of 1,425 presumptive viremic donors were reported to CDC from 41 states. Of 36 investigations of suspected WNV TAT in 2003, 6 cases were documented. Estimated viremia levels were available for donations implicated in four TAT cases; the median estimated viremia was 0.1 plaque-forming units (PFUs) per mL (range, 0.06-0.50 PFU/mL; 1 PFU equals approximately 400 copies/mL).


CONCLUSIONS
National blood screening for WNV identified and removed more than 1,400 potentially infectious blood donations in 2003 through 2005. Despite the success of screening in 2003, some residual WNV TAT risk remained due to donations containing very low levels of virus. Screening algorithms employing selected individual-donation testing were designed to address this residual risk and were fully implemented in 2004 and 2005. Continued vigilance for TAT will evaluate the effectiveness of these strategies.
Montgomery
Susan P
SP
Division of Vector-Borne Infectious Diseases, Centers for Disease Control and Prevention, Fort Collins, Colorado, USA. SMontgomery@cdc.gov
Brown
Jennifer A
JA
Kuehnert
Matthew
M
Smith
Theresa L
TL
Crall
Nicholas
N
Lanciotti
Robert S
RS
Macedo de Oliveira
Alexandre
A
Boo
Thomas
T
Marfin
Anthony A
AA
D000293:Adolescent; D000368:Aged; D000369:Aged, 80 and over; D001782:Blood Donors; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D021141:Nucleic Acid Amplification Techniques; D013997:Time Factors; D065227:Transfusion Reaction; D014481:United States / Q000453:epidemiology; D014901:West Nile Fever / Q000453:epidemiology / Q000635:transmission*