- Varicella-zoster virus (VZV) is a highly contagious, double-stranded DNA virus that belongs to the Herpesviridae family, specifically the Alphaherpesvirinae subfamily.
- It is the causative agent of two distinct clinical diseases: varicella (chickenpox), which occurs during primary infection, and herpes zoster (shingles), which results from reactivation of latent virus later in life. VZV is exclusively a human pathogen and has a global distribution, with widespread childhood infection in areas without routine vaccination.
- Primary VZV infection, usually acquired in childhood, leads to varicella, a generalized illness characterized by fever, malaise, and a distinctive itchy vesicular rash that typically starts on the trunk and spreads to the limbs and face.
- Transmission occurs via respiratory droplets or direct contact with vesicular fluid from skin lesions. The virus first replicates in the upper respiratory tract, then spreads through the bloodstream (viremia) to the skin and other organs. While chickenpox is usually self-limited in healthy children, it can cause serious complications such as pneumonia, encephalitis, and bacterial superinfection, particularly in adults, pregnant women, and immunocompromised individuals.
- After resolution of the primary infection, VZV establishes latency in sensory nerve ganglia, such as the dorsal root or cranial nerve ganglia. The virus can remain dormant for decades, controlled by the host immune system. Reactivation of VZV later in life leads to herpes zoster, or shingles, a painful, localized skin eruption that follows the distribution of a single dermatome. This reactivation is more common with increasing age or in individuals with weakened immune systems. Herpes zoster may be accompanied by postherpetic neuralgia (PHN)—a chronic, debilitating nerve pain that can persist long after the rash resolves.
- Diagnosis of VZV infections is often clinical, especially for varicella, given its characteristic rash. For more complex cases or immunocompromised patients, polymerase chain reaction (PCR) testing, direct fluorescent antibody tests, or serology may be used to confirm VZV infection or immunity. Tzanck smear can show multinucleated giant cells, although it cannot distinguish between herpes simplex and VZV.
- Vaccination has significantly reduced the incidence and severity of both varicella and herpes zoster. The live attenuated varicella vaccine, introduced in the 1990s, is now routinely administered to children in many countries. A higher-potency version of the vaccine is used as the zoster vaccine to prevent shingles in older adults. More recently, a recombinant subunit zoster vaccine (Shingrix) has been developed and is preferred in many settings due to its superior efficacy and safety profile, especially in the elderly and immunocompromised populations.
- Treatment of VZV includes supportive care for mild varicella, while antiviral medications such as acyclovir, valacyclovir, or famciclovir are used to reduce the severity and duration of symptoms in moderate to severe cases or those at higher risk of complications. For herpes zoster, early antiviral therapy helps shorten the duration of symptoms and may reduce the risk of postherpetic neuralgia. Pain management for PHN often includes neuropathic pain agents such as gabapentin, pregabalin, or tricyclic antidepressants.
