ReviewVaricella-zoster virus and virus DNA in the blood and oropharynx of people with latent or active varicella-zoster virus infections

•VZV viremia occurs −5 to +4 days of varicella; VZV DNAemia occurs at −8/−10 to +7 days.•VZV DNA in blood/saliva is useful for diagnosis and prognosis of atypical varicella.•VZV DNAemia is present at the onset of herpes zoster and for many weeks thereafter.•VZV DNA in blood/saliva facilitates the diagnosis of atypical cases of herpes zoster.

Varicella-zoster virus (VZV) can be detected in the blood from approximately 5 days before to 4 days after varicella. VZV DNA, primarily in T-lymphocytes, is detected as early as 8-10 days prior to rash and can persist for a week. The duration and magnitude of VZV DNAemia correlates with immune status and the efficacy of antiviral therapy. VZV DNA is also readily detected in the oropharynx just prior to rash and for 1-2 weeks thereafter. Detection of VZV DNA in blood and saliva has been useful for diagnosis and prognosis in atypical cases of varicella. Herpes zoster (HZ) is also characterized by VZV DNAemia at onset and for many weeks thereafter, and VZV DNA is present in the oropharynx shortly after HZ onset. Detection of VZV DNA in blood and saliva facilitates the diagnosis of zoster sine herpete and other atypical manifestations of VZV reactivation, such as neurologic syndromes when cerebrospinal fluid is not available, Bell's palsy, and atypical pain syndromes. VZV DNA is sometimes present in the blood and saliva of asymptomatic individuals. In total these observations extend understanding of the pathophysiology and epidemiology of VZV, and increasingly contribute to the clinical management of VZV infections.