The current diagnosis of West Nile Virus (WNV) infection is primarily based on serology since molecular identification of WNV RNA is unreliable due to the short viremia and absence of detectable virus in cerebrospinal fluid (CSF). Recent studies have shown that WNV RNA can be detected in urine for a longer period of time and at higher concentrations than plasma. Here, we examined the presence of WNV RNA in serum, plasma, whole blood, CSF and urine samples obtained from acute WNV infection diagnosed patients during an outbreak which occurred in Israel in 2015. Our results demonstrate that 33 of 38 WNV patients had detectable WNV RNA in whole blood at the time of diagnosis, a higher rate than detection of WNV RNA in any of the other sample types tested. Overall, whole blood was superior to all other samples with 86.8% sensitivity, 100% specificity, 100% positive predictive value and 83.9% negative predictive value. Interestingly, WNV viral load in urine was higher than in whole blood, CSF, serum and plasma despite the lower sensitivity compared to whole blood. This study establishes the utility of whole blood in the routine diagnosis of acute WNV infection and suggests that it may provide the highest sensitivity for WNV RNA detection in suspected cases.
Superiority of West Nile Virus RNA detection in whole blood for diagnosis of acute infection.