Click here to view next page of this article
Varicella-zoster virus (VZV) causes varicella, the most common exanthematous disease of childhood. After the acute infection, VZV remains latent in the dorsal root ganglia; reactivation of the virus later in life causes zoster. VZV is ubiquitous, and humans are the only known host. It is estimated that there are 4 million cases per year in the United States, of which 90% occur in children between the ages of 1 and 14 years. Seropositivity reaches 95% by the late teen years and is close to 100% by age 60. The virus is highly contagious, with secondary household infection rates of about 80% to 90%. In temperate climates, a seasonal peak occurs between March and May. There are approximately 6,500 to 9,000 hospitalizations and 100 to 200 deaths in the United States annually from chicken pox, zoster and shingles.
The primary source of infectious material is the fresh cutaneous lesion, which is teeming with virus. Unlike the poxviruses, VZV does not persist in scabs or crusts. It generally is believed that the period of communicability begins 1 to 2 days before the onset of rash and persists for 5 days or until skin lesions.
VZV is an alpha-herpesvirus. Like all herpes group viruses, it is an enveloped, icosahedral virus that contains a double-stranded DNA genome. Chickenpox begins with replication of the virus at sites.
Primary infection with VZV produces the well-known clinical syndrome of varicella or chickenpox. Low-grade fever may precede the development of the rash by 1 to 2 days. The characteristic rash involves lesions that appear in crops and proceed through a series of well-defined stages.
Prenatal infection is uncommon because most women of childbearing age are immune to varicella. Although rare, a congenital varicella syndrome occurs in nearly 2% of infants.
Early studies suggested that the risk of death was as high as 31% among infants whose mothers.
Varicella in the immunocompromised host can be severe and life-threatening. Cell-mediated immunity appears to be the most important factor in the prognosis of primary varicella infection.
The most common complication of primary varicella is bacterial superinfection of pox lesions. Cellulitis, impetigo, or adenitis can be seen. These infections usually are caused by staphylococcal or streptococcal species and sometimes are mixed. In recent years, an increasing number of reports.
Central nervous system complications also are seen in varicella. Cerebellar ataxia is the most common, with an incidence of approximately 1 per 4,000 cases in children younger than 15 years of age.
Varicella pneumonia is the third most common complication and occurs much more frequently.
Hemorrhagic varicella is seen occasionally, and there are several forms. Hemorrhage at sites of pox lesions does not always herald a more severe course.
Reye syndrome, which presents with persistent vomiting and decreasing mental status, has been associated with varicella more frequently than with other viral infections.
Mono- or polyarticular arthritis has been reported with VZV infection, and the virus has been grown.
Zoster or shingles is a disease that increases in frequency with advancing age, but it can be seen at any age, including in neonates. It is three times more common among adolescents than it is among preschoolers. Children who contract varicella in the first year of life have a 3- to 20-fold increased risk.
Acute, uncomplicated varicella in the young child is managed best by topical antipruritics such as calamine lotion, application of cool compresses, or by oatmeal baths.
In 1978, VZIG prepared from the plasma of normal volunteers identified by routine screening to contain high antibody titers to VZV became available. Administration of VZIG to exposed individuals may prevent or reduce the intensity of disease. A carefully documented history of chickenpox.
The live attenuated varicella vaccine was attenuated by propagation in human embryonic lung fibroblasts, guinea pig embryonic cells, and finally in two different cell lines of human diploid cell cultures. The varicella vaccine has been tested extensively in the United States.