West Nile virus nucleic acid persistence in whole blood months after clearance in plasma: implication for transfusion and transplantation safety.

BACKGROUND: Previous reports of West Nile virus (WNV) RNA persistence in blood compartments have raised concerns around the remaining risk of WNV transfusion transmission. This study characterized the dynamics of WNV viremia in blood compartments in a longitudinal cohort of 54 WNV-infected blood donors. STUDY DESIGN AND METHODS: Blood samples were collected throughout the year after WNV RNA-positive blood donation (index) and characterized for WNV immunoglobulin (Ig)M and IgG antibodies and for WNV RNA by real-time reverse transcription-polymerase chain reaction. WNV viral loads were compared in plasma and whole blood samples and correlated with blood groups and clinical outcomes. RESULTS: WNV RNA persisted in the red blood cell (RBC) compartment up to 3 months postindex in 42% of the donors. Donors with the highest WNV RNA levels in plasma at index maintained the highest WNV RNA levels in whole blood over the 3 months postindex. Blood group A donors maintained higher postindex WNV viral load in whole blood than blood group O individuals (p = 0.027). Despite a trend for WNV RNA to persist longer in whole blood from symptomatic subjects, no significant association was found between WNV RNA levels in whole blood and disease outcome. CONCLUSION: This study confirmed that WNV RNA persists in the RBC fraction in whole blood and further suggested that the level of persistence in whole blood may be a reflection of initial viral burden in plasma. The association with blood groups suggests that WNV adherence to RBCs may be mediated by molecules overrepresented at the surface of blood group A RBCs.

Associations between West Nile virus infection and symptoms reported by blood donors identified through nucleic acid test screening.

BACKGROUND: Blood collected in the United States and Canada is screened for West Nile virus (WNV) using nucleic acid testing (NAT). The role that donor-reported symptoms of infection disclosed at or shortly after donation may play in enhancing blood safety has been debated. Little data are available on subsequent manifestations of WNV-specific disease outcomes in viremic donors. STUDY DESIGN AND METHODS: Donors with initially reactive NAT results were informed by telephone and asked to complete symptom interviews. The questionnaires are focused on three time periods: the week before, the day of, and the 2 weeks after donation. Symptoms and risk factors were compared between confirmed-positive and false-positive donors (classified based on confirmatory NAT and serology). Additional analyses comparing confirmed-positive symptomatic and asymptomatic donors were conducted. RESULTS: A total of 423 of 536 initially reactive donors were interviewed between 2003 and 2006: 292 confirmed-positive for WNV and 131 false-positive. Individual symptoms were not significant predictors of WNV infection, except skin rash in the week before donation (odds ratio [OR], 3.0; 95% confidence interval [CI], 1.2-7.9) and body aches in the period after donation (OR, 2.8; 95% CI, 1.1-7.4). Specific combinations of symptoms were not good predictors of infection, but donors with three or more concurrent symptoms before donation were more likely to have WNV infection (OR, 2.5; 95% CI, 1.2-5.1). Demographic characteristics, predonation symptoms, and serology profiles in confirmed-positive donors did not predict postdonation symptom severity. Thirty-five confirmed-positive donors (12%) sought medical care for WNV infection, with two hospitalizations, but no cases of neuroinvasive disease. CONCLUSION: The number rather than type of symptoms is associated with confirmed WNV infection, but the overall predictive value is low. Very few infected donors develop clinically significant disease.