Varicella-zoster virus (VZV) is one of eight herpesviruses known to cause human infection and is endemic worldwide. VZV infection causes two clinically distinct diseases: varicella (chickenpox) and herpes zoster (shingles). Transmission occurs via contact with aerosolized droplets from nasopharyngeal secretions of an infected individual or by direct cutaneous contact with vesicle fluid from skin lesions. The average incubation period for primary infection with VZV is 14 to 16 days although it can extend to 21 days in cases.

The diagnosis of VZV infection is usually a clinical diagnosis based on the characteristic vesicular lesions, which are seen widespread in chickenpox or in a restricted dermatomal pattern with associated neuritis in shingles. Additional diagnostic information may be useful where there is an atypical rash in an immunocompromised host or possible disseminated disease in an immunosuppressed host without cutaneous lesions. In addition, serologic testing may be necessary to determine if an individual at increased risk for varicella requires immunisation (e.g., a healthcare worker).