Varicella‑Zoster Virus (VZV, HHV‑3) is an enveloped double‑stranded DNA virus belonging to the *Varicellovirus* genus of the Alphaherpesvirinae subfamily. It causes varicella (chickenpox) during primary infection and remains latent in sensory ganglia, with later reactivation manifesting as herpes zoster (shingles).
Biology and Disease Mechanisms
VZV has an icosahedral capsid, tegument and lipid envelope containing glycoproteins that mediate attachment to heparan sulfate and mannose receptors on epithelial and immune cells. After transmission via respiratory droplets or direct contact, the virus infects the respiratory mucosa and regional lymph nodes. It disseminates through viremia to the skin, where it replicates in keratinocytes and causes the characteristic vesicular lesions of chickenpox. The 125 kilobase genome replicates in the nucleus using host polymerase; immediate early, early and late genes coordinate replication and assembly. After the primary infection resolves, VZV establishes latency in cranial nerve, dorsal root and autonomic ganglia. Reactivation involves anterograde transport of virions along sensory nerves to the skin, resulting in shingles, typically confined to a single dermatome. Reactivation is more common in older adults and immunocompromised individuals. Antiviral drugs such as acyclovir, famciclovir and valacyclovir inhibit viral DNA polymerase and reduce severity if given early, but the virus is never eliminated.
Clinical Features and Vaccination
Primary varicella presents with fever, malaise and a generalized pruritic rash that progresses from macules to vesicles before crusting. Complications may include bacterial superinfection, pneumonia, cerebellar ataxia and encephalitis. Maternal infection during the first two trimesters can cause congenital varicella syndrome, while peripartum infection may lead to severe neonatal disease. Herpes zoster occurs years later as a unilateral painful vesicular eruption along a dermatome, often accompanied by neuropathic pain that can persist as postherpetic neuralgia. Ophthalmic involvement may threaten vision. A live attenuated varicella vaccine has greatly reduced chickenpox incidence and is recommended universally in childhood, and a higher‑dose recombinant glycoprotein E vaccine is advised for adults to prevent shingles and its complications. Exposed susceptible pregnant women and immunocompromised patients may receive varicella‑zoster immune globulin. Good infection control and prompt antiviral therapy remain important, especially in high‑risk groups. VZV is unique among herpesviruses in that it spreads predominantly through airborne transmission and causes both a childhood exanthem and a late‑life neuropathic disease. Effective vaccination has transformed its epidemiology, but vigilant management of reactivation and protection of vulnerable populations remain essential. Related Terms: herpes zoster, chickenpox, latency, vaccine, dorsal root ganglion