VZV

Varicella-zoster virus (VZV) is a human alphaherpesvirus in the family Herpesviridae. It is a linear double-stranded DNA virus with a genome of about 125 kilobases and around 70 encoded genes. VZV causes two clinically distinct diseases: varicella (chickenpox) as a primary infection and herpes zoster (shingles) upon reactivation. Following primary infection, the virus establishes latency in sensory dorsal root and cranial nerve ganglia.

Transmission occurs mainly via respiratory droplets or direct contact with vesicular fluid. Primary varicella is highly contagious and can be acquired by susceptible individuals, including unvaccinated children. After recovery, VZV remains latent in ganglia and can reactivate later in life, often with aging or immunosuppression as triggers, producing herpes zoster, a painful, unilateral vesicular eruption in a dermatomal distribution. Rare disseminated zoster can occur in severely immunocompromised individuals.

Clinical features and complications: Varicella presents with a generalized pruritic vesicular rash in successive crops, fever, and malaise. Shingles presents with localized pain and a vesicular rash in a dermatomal pattern. Complications include pneumonia, encephalitis, bacterial skin infection, hepatitis, and in pregnancy, congenital varicella syndrome if infection occurs during gestation; neonatal varicella can occur with perinatal infection.

Diagnosis and management: Diagnosis is clinical but can be confirmed by PCR testing of vesicular fluid or serology. Antiviral medications such as acyclovir, valacyclovir, or famciclovir are most effective when started early. Prevention relies on vaccination: varicella vaccine (two-dose schedule) provides protection against primary varicella, and the recombinant zoster vaccine or the live attenuated shingles vaccine reduces risk of herpes zoster and its complications.