Varicellazoster Virus VZV

Pathogen, pathogenesis, clinical picture. The VZ virus differs substantially from HSV, both serologically and in many biological traits. For instance, it can only be grown in primate cell cultures, in which it grows much more slowly and more cell-associated than is the case with HSV. No subtypes have been described.

422 8 Viruses as Human Pathogen — Herpes zoster-

422 8 Viruses as Human Pathogen — Herpes zoster-

Varicella Zoster Virus Vzv Structure
Fig. 8.6 The varicella zoster viruses (VZV) persist in the latent state in spinal ganglia cells. When reactivated, they cause dermal efflorescences in the corresponding dermatome.

The initial infection with VZV manifests in the great majority of persons as chickenpox, an episodic papulous exanthem. The portals of entry are the nasopharyngeal space and the conjunctiva. From there, the virus undergoes a viremic phase in which it is transported by the blood to the skin, where the typical exanthem is produced. The disease confers an effective immunity. In immunodeficient patients, a VZV infection (or reactivation, see below) can affect other organs (lungs, brain) and manifest a severe, frequently lethal, course.

After the symptoms of chickenpox have abated, the VZV persists in the spinal ganglia and perhaps in other tissues as well. Following reactivation, zoster (shingles) develops (Fig. 8.6), whereby the virus once again spreads neurogenically and causes neuralgia as well as the typical zoster efflorescence 8 in the skin segment supplied by the sensitive nerves. Reactivation is induced by internal or external influences and becomes possible when cellular VZV immunity drops off, i.e., after about the age of 45 assuming normal immune defenses.

Diagnosis. VZV can be detected with a wide spectrum of methods, namely PCR, isolation, direct viral detection by means of electron microscopy, detection of viral antigens using immunofluorescence in tissue specimens or cell smears, and serologically based on antibody titer increases or IgM detection.

Epidemiology, prevention, and therapy. VZV is highly contagious and is transmitted aerogenically. The primary infection, which manifests as chick-enpox, is still almost exclusively a childhood disease today. A vaccine containing attenuated viruses is available for prevention of chickenpox and possibly zoster, but its use is currently a matter of controversy. In immunosuppressed patients, hyperimmunoglobulin can be used for passive immunization or postexposure immunity. Acycloguanosine is used both prophylactically and in treatment of VZV infections.

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Essentials of Human Physiology

Essentials of Human Physiology

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