Varicella Zoster Virus (VZV) VZV is one of eight herpes viruses and commonly causes chickenpox in children, teens and young adults and herpes zoster (shingles) in adults. It is usually a mild disease that lasts a short time in healthy children. However, it can be severe in adults and may cause serious and even fatal complications in people of any age.
VZV infects the nerves causing a wide variety of symptoms and two clinically distinct forms of disease. Primary infection results in chickenpox and recurrent infections leads to herpes zoster (shingles). Symptoms of VZV are exhibited between 10 and 21 days after infection. The main symptom is a rash that turns into open lesions which crust over. It is spread through the airborne route primarily from the skin vesicles. The immunologic mechanism that controls latency of VZV is not well understood, however factors associated with recurrent disease include aging, immunosuppression, intrauterine exposure to VZV, and having had varicella at a young age (younger than 18 months). Infection with VZV is generally mild and self-limited, but it may be associated with complications, especially in adults or children under 1-year old. Secondary bacterial infections of skin lesions with Staphylococcus or Streptococcus are the most common cause (5% of cases) of hospitalization and invasive group A streptococci can lead to serious illness or death. Other complications include secondary pneumonia (bacterial or viral), aseptic meningitis, encephalitis, myocarditis and arthritis. A more rare complication is Reye’s syndrome and occurs almost exclusively in children who take aspirin during the acute illness. Routine vaccination against VZV is performed in the United States and Japan, however most countries still do not vaccinate. It is now available
VARICELLA VIRUS
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as a quadrivalent measles-mumps-rubella- varicella (MMRV) vaccine and it is gaining wider acceptance globally. The VZV vaccine is on the World Health Organization’s (WHO) List of Essential Medicines, a list of the most important medications needed in a basic health system.
DIAGNOSIS The clinical presentations of VZV are very characteristic, however diagnosis is important for determining the immune status before prognostic and therapeutic monitoring. Several methods exist including polymerase chain reaction (PCR), direct immunofluorescent assay (DFA), viral isolation and serologic assays that detect VZV-specific antibodies. Recent infection is suggested by the detection of serum VZV-specific IgM antibodies, but this can be less reliable for herpes zoster where specific antibodies are already present. The National VZV Laboratory at the CDC has developed a reliable IgM capture assay. Other current commercials assays for determining VZV immune status include ELISAs, latex agglutination, indirect-immunofluorescence assay (IFA) and enzyme-linked fluorescent immunoassay (ELFAs). Primary maternal varicella infection in the first 20 weeks of gestation is associated with a variety of abnormalities in the newborn collectively known as congenital varicella syndrome. The range and severity of associated symptoms and physical findings may vary greatly from case to case depending upon when the maternal varicella zoster infection occurred during fetal development. In general, newborns with congential VZV have a low birth weight, distinctive skin abnormalities, and brain malformations. CONGENITAL VZV INFECTION
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ToRCH & Childhood Diseases- Reagents for Assay Development
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