[Primary varicella-zoster virus infection--current knowledge, diagnostic and therapeutic approaches]

Abstract

Introduction: It is well known that varicella, a clinical entity of primary varicella-zoster virus infection, is most commonly a mild, benign disease of preschool and school children. However, in spite of progress in diagnostic approach and up-to-date treatment based on specific antiviral agents, many clinicians face cases of life-threatening varicella with uncertain course and prognosis, in adult and immunocompromised patients predominantly. ETIOPATHOGENESIS AND HISTOPATHOLOGY: Varicella-zoster virus (VZV) is a member of the Herpesviridae family. The portal of entry is nasopharyngeal mucosa, sometimes conjunctiva. VZV causes a generalized infection and has dermal tropism. Histopathological findings include degenerative changes of epithelial cells such as ballooning, multinucleated giant cells and eosinophilic intranuclear inclusions. CLINICAL FEATURES AND COMPLICATIONS: The evolution of varicella includes 3 stages of disease and is characterized by gradual onset, constitutional symptoms, signs of upper respiratory tract and polymorphous rash. According to the severity of clinical presentation, there is a number of mild forms and severe, even life-threatening forms of varicella. According to etiology, varicella complications are divided in viral and bacterial ones. Immunocompromised patients often develop serious, life-threatening forms of varicella. Especially the prognosis of visceral dissemination commonly followed by liver and brain involvement is dubious. The course of varicella in pregnancy may be severe because of changed immune response and more frequent appearance of complications in adults. The probability of vertical transmission of VZV is 25%. The early infection of embryo may lead to abortion. The symptomatic intrauterine infection appears in about 3% of all cases of varicella of pregnant women and is called a "congenital varicella syndrome". Vertical transmission of VZV in the late pregnancy may result in preterm delivery or perinatal varicella (varicella in the newborn).

Diagnosis: The diagnosis is made by history and physical examination. Atypical cases of varicella require laboratory confirmation of diagnosis including virus/viral antigen detection, virus isolation and identification or serological diagnosis (detection of specific anti-VZV antibodies in patient's sera).

Prevention: Prevention of varicella includes active and passive immunization. Passive immunization is based on the use of varicella-immunoglobulin (VZIG). A live, attenuated vaccine was developed by Takahashi and colleagues in Japan. This vaccine is recommended, first of all, to seronegative immunodeficient children. Vaccine virus is sensitive to acyclovir and is not transmissible to non-vaccinated children. The duration of vaccine-induced immunity is at least 6-10 years in the majority of vaccinees.

Therapy: Hygiene is the most important principle in the management of varicella, particularly bathing and use of a stringent soaks to avoid secondary bacterial skin infection. The patient should be isolated in a well-ventilated room with regular change of bed, linen and light food should be provided. Indications for, acyclovir (and other antiviral agents) treatment are, individuals who have suffered from severe forms of varicella and those, belonging to the high-risk group of patients (adults, viral, complications, immunocompromised host).