Epidemiology, clinical manifestations, and diagnosis

●Infections caused by varicella-zoster virus (VZV)

Varicella-zoster virus (VZV) infection causes two distinct diseases. Primary infection with VZV results in varicella (chickenpox), characterized by vesicular lesions in different stages of development on the face, trunk, and extremities. Herpes zoster, also known as shingles, results from reactivation of latent VZV infection within the sensory ganglia. 

●Risk factors for herpes zoster infection

The incidence of herpes zoster is influenced by the immune status of the host, age-related immunosenescence, disease-related immunocompromise, or iatrogenic immunosuppression, with age being the major risk factor for 90 percent of cases of herpes zoster in adults. 

●Risk of transmitting VZV to others

People with herpes zoster can spread VZV to those who have not had varicella and have never received the varicella vaccine. The virus can spread through direct contact with herpes zoster lesions (the lesions are considered infectious until they dry and crust over). Airborne transmission of VZV from individuals with localized herpes zoster also occurs. 

●Clinical manifestations of herpes zoster

The presenting clinical manifestations of herpes zoster are usually characterized by rash and acute neuritis. The thoracic and lumbar dermatomes are the most commonly involved sites of herpes zoster, although any dermatome can be affected. 

Immunocompromised hosts are at risk for cutaneous and visceral dissemination.

●Complications of herpes zoster

The most common complication of herpes zoster is postherpetic neuralgia. Other complications include herpes zoster ophthalmicus or oticus, and less commonly acute retinal necrosis, aseptic meningitis, and encephalitis. 

●Approach to diagnosis

In immunocompetent individuals, the diagnosis of herpes zoster is usually based on the clinical presentation (ie, unilateral, usually painful, vesicular eruption with a well-defined dermatomal distribution). However, when the diagnosis is uncertain, laboratory confirmation is indicated. Diagnostic techniques include the polymerase chain reaction (PCR) assay (which is the most sensitive test), direct fluorescent antibody testing, and viral culture.