Primary
infection with varicella zoster virus (VZV) occurs in immunocompromised and immunocompetent individuals. Clinical and asymptomatic reactivation with shedding of infectious virus and
viremia may occur. The prevalence of VZV
viremia is unknown. The aim of this study was to detect VZV
viremia and quantify VZV
DNA using quantitative polymerase chain reaction (qPCR) in blood from different populations. A qPCR-based method using EvaGreen® was used to quantify VZV
DNA in 491 samples, including whole blood, plasma and buffy-coat, from patients hospitalized with
varicella-associated disease (Group 1, n=10) and three groups with no VZV disease: individuals with a first clinical diagnosis of central nervous system
demyelination (Group 2, n=213) with their age and sex-matched controls (Group 3, n=218); and HIV-infected individuals (Group 4, n=50). VZV-specific
IgG antibody titres were measured in Group 3. The proportion positive for
viremia and mean detectable VZV
DNA load (copies/ml) were: Group 1: 100% (10/10) and 4.6 × 10(6) ± 1.4 × 10(7) ; Group 2: 4% (9/213) and 1.5 × 10(3) ± 1.8 × 10(4) ; Group 3: 8% (17/218) and 1.1 × 10(3) ± 7.8 × 10(3) ; Group 4: 12% (6/50) and 7.7 × 10(1) ± 2.8 × 10(2) . VZV
DNA load and
IgG titres were not significantly correlated (Group 3 only). VZV load in Group 1 was significantly elevated compared to Groups 2-4 (P<0.001); the latter were not significantly different from each other (P=0.05). VZV genotypes from clades 1-5 were identified in Group 1. VZV
DNA was detected but at low frequency and viral load in both immunocompetent and immunocompromised individuals asymptomatic for VZV
infection, compared to individuals with active VZV
infection.