Incidence of West Nile virus infection in the Dallas-Fort Worth metropolitan area during the 2012 epidemic.

The 2012 West Nile virus (WNV) epidemic was the largest since 2003 and the North Texas region was the most heavily impacted. We conducted a serosurvey of blood donors from four counties in the Dallas-Fort Worth area to characterize the epidemic. Blood donor specimens collected in November 2012 were tested for WNV-specific antibodies. Donors positive for WNV-specific IgG, IgM, and neutralizing antibodies were considered to have been infected in 2012. This number was adjusted using a multi-step process that accounted for timing of IgM seroreversion determined from previous longitudinal studies of WNV-infected donors. Of 4971 donations screened, 139 (2·8%) were confirmed WNV IgG positive, and 69 (1·4%) had IgM indicating infection in 2012. After adjusting for timing of sampling and potential seroreversion, we estimated that 1·8% [95% confidence interval (CI) 1·5-2·2] of the adult population in the Dallas-Fort Worth area were infected during 2012. The resulting overall estimate for the ratio of infections to reported WNV neuroinvasive disease (WNND) cases was 238:1 (95% CI 192-290), with significantly increased risk of WNND in older age groups. These findings were very similar to previous estimates of infections per WNND case, indicating no change in virulence as WNV evolved into an endemic infection in the United States.

Distribution of hepatitis C virus in circulating blood components from blood donors.

BACKGROUND AND OBJECTIVES: Current nucleic acid tests (NAT) for blood donor screening use plasma as the test sample and, consequently, cannot detect virions bound to blood cells of infected donors. Hepatitis C virus (HCV) RNA and infectious virions have been detected in association with the cellular components of blood of patients with active liver disease; however, studies comparing HCV viral loads in whole blood and plasma have generated contradictory results. The aim of this study was to investigate the distribution of HCV in different compartments of the peripheral blood from HCV-infected blood donors, which may differ from that observed in patients with HCV-associated liver disease. MATERIALS AND METHODS: Hepatitis C virus-positive donor specimens were identified by NAT and antibody testing. HCV RNA was extracted from samples of whole blood and their corresponding components (RBC and plasma). Viral RNA was quantified by real-time qRT-PCR. RESULTS: Hepatitis C virus was present in all blood components from infected donors from which RNA could be amplified. For the majority of samples, plasma (34/46) had the highest detectable concentration of HCV RNA, and RBC (37/46) had the lowest. Specimens with negative NAT and positive antibody assays also produced qRT-PCR negative results. CONCLUSION: These results indicate that including the RBC fraction in the tested sample will not increase assay sensitivity. Although 10% of the specimens had a higher viral load in whole blood, there was no significant overall increase in sensitivity to justify changes in the specimen format. Thus, plasma specimens are well suited for blood donor screening for HCV.