VarizellaZosterVirus

Varicella-zoster virus (VZV) is a human alphaherpesvirus in the family Herpesviridae. It is a linear double-stranded DNA virus with an enveloped icosahedral capsid and genome around 125 kilobases encoding roughly 70 proteins. VZV establishes infection in humans and is the cause of two distinct diseases: primary varicella (chickenpox) and reactivation to herpes zoster (shingles). Transmission occurs mainly via respiratory droplets or direct contact with vesicular fluid.

Following primary infection, VZV typically causes varicella in children, though it can affect individuals of any age. The incubation period is usually 10 to 21 days. The illness presents with fever, malaise, and a pruritic vesicular rash that evolves from macules to vesicles before crusting. After resolution, the virus remains latent in sensory dorsal root and cranial nerve ganglia.

Reactivation later in life leads to herpes zoster, usually as a painful, unilateral dermatomal rash. Shingles can be accompanied by sensory symptoms such as allodynia and may result in postherpetic neuralgia, particularly in older adults. Complications are more common in immunocompromised individuals and can include disseminated disease, pneumonia, or encephalitis.

Prevention relies on vaccination and infection control. Varicella vaccination (live attenuated) is given in childhood in many countries and reduces varicella incidence and transmission. For adults, shingles prevention is increasingly achieved with recombinant zoster vaccines (e.g., Shingrix), with live vaccines available in some settings. Diagnosis is usually clinical but can be confirmed by PCR testing of lesion fluid or serology. Antiviral therapy (acyclovir, valacyclovir, or famciclovir) is most effective when started early in both varicella and shingles.