varicella zoster virus (V-Z)

The varicella-zoster virus (VZ) can cause a highly contagious mild disease in children - chickenpox, which manifests itself in the development of a vesicular rash on the skin and mucous membranes. In adults (and very rarely in children), the same virus causes shingles (zoster), characterized by an inflammatory reaction in the dorsal roots of the spinal cord and in the ganglia; it is accompanied by a rash of blisters on the skin in the area innervated by the affected sensory nerve. Chickenpox is considered a reaction to the primary contact of the virus with the human body, while zoster is a response of the partially immune host to the reactivation of the virus, present in a latent form in the sensory ganglia.

This virus is identical to the herpes simplex virus in morphological, biological and even antigenic properties, but it does not reproduce in the body of laboratory animals. It affects human cells: often visible is the arrest of division in metaphase, shrinkage of chromosomes, rupture of chromosomes and formation of micronuclei.

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Pathogenesis and symptoms of chickenpox

The VZ virus is transmitted by airborne droplets; the source of infection is a sick person. Primary reproduction of the virus occurs in the epithelium of the mucous membrane of the upper respiratory tract. Then, via the lymphatic route, the virus penetrates the bloodstream, and with it, the skin. Epithelial cells swell, ballooning degeneration (dystrophy) of the cells of the spinous layer is observed, the accumulation of tissue fluid leads to the formation of bubbles. Eosinophilic inclusion bodies are found in the nuclei of affected cells, especially in the early stages. In addition to this, with shingles, there is an inflammatory reaction in the posterior roots of the spinal cord and sensory ganglia. The incubation period for chickenpox is 14-21 days, while for shingles it is unknown. Chickenpox begins with malaise, fever, a rash on the face, then on the trunk and limbs. First, an itchy spot appears, which quickly turns into a blister filled with a serous-cloudy liquid. Then the blister bursts, a crust forms in its place, which subsequently falls off and leaves no scar. The rash of new blisterings continues for 3-4 days, their contents include a huge amount of virus. Mortality and complications (encephalitis, pneumonia) are quite rare, more often observed in newborns. In the first three months of pregnancy, chickenpox in women can lead to congenital deformities of the fetus.

With shingles, following the malaise and fever, severe pain appears in the area of the mucous membrane or skin innervated by one or more groups of sensory ganglia. After a few days, blisters appear in this area. Most often, this is observed on the trunk (along the intercostal nerve), on the scalp or neck.

Laboratory diagnostics of chickenpox

It is carried out in the same way as the diagnosis of herpes simplex, but the following points should be taken into account. The herpes simplex virus causes the development of lesions in the cornea of rabbits, the brain of mice and the chorion-allantoic membrane of the chicken embryo, while the VZ virus almost does not infect the specified tissues. In most cell cultures, the herpes simplex virus grows quickly, forming plaques in 18-24 hours. The VZ virus grows mainly in fibroblast cells for 3-5 days. These viruses differ in the morphology (mainly in size) of the virions in the vesicular fluid during electron microscopy, as well as in the presence of an antigen in the vesicular fluid, detected by the method of immunodiffusion in a gel with specific precipitating sera (against herpes viruses, VZ and vaccinia).

Treatment of chickenpox

Gamma globulin obtained from the serum of patients with shingles in the recovery stage has a good therapeutic effect. This drug can also be used to prevent chickenpox in contact children with immunodeficiency conditions.