Varicella-zoster virus (VZV) is one of the DNA virus forms. Chickenpox and shingles can be caused by it. VZV is a herpes virus.
What is varicella-zoster virus?
Humans are the only natural hosts of these herpes viruses. They have a worldwide distribution. The varicella-zoster virus is enveloped in a membrane. This membrane contains a double-stranded DNA. Furthermore, the virus consists of an icosahedral capsid. This is a small capsule composed of a fixed number of protein units. The capsid of VZV contains 162 capsomeres. A viral unit has a maximum diameter of 200 nm. Varicella zoster virus belongs to the genus Varicellovirus and is closely related to herpes simplex virus. Approximately 95 percent of the population has antibodies to this virus.
Significance and function
Varicella zoster virus is highly contagious. Through droplet infection, VZV is transmitted very quickly and easily. On first contact with the pathogen, it leads to varicella – infection, also known as chickenpox. The name formed because of the high risk of infection. Even a few meters away, the viruses can be contagious “over the wind” as droplet infection. Chickenpox predominantly affects young children who have not yet been vaccinated. Chickenpox is therefore also classified as a childhood disease. The incubation period of the disease is normally 14 – 16 days. About 2 days before the rash becomes visible, affected patients become contagious. The risk of infection continues until the blisters are crusted on the skin. The disease begins with fever and itchy skin rash (exanthem). The skin lesions are the typical feature of the disease. These exanthemas consist of papules, vesicles and scabs. They are in different stages of development and are also called “starry skies”. These skin lesions develop on the face and the middle of the body. Later they may spread to other parts of the body, affect persistent scalp or even mucous membranes. Normally, chickenpox heals without scarring. However, if a bacterial superinfection occurs or if the rash is scratched hard, scarring may occur. Diseases with chickenpox are characterized by a typical clinical picture. Special diagnostics are required only in selected cases.
Varicella zoster virus hazards, disorders, risks, and diseases.
In particular, people with immunodeficiencies can be affected in a life-threatening manner. Very dangerous is the infection of chickenpox also during pregnancy. Infections of the fetus before the 20th week of pregnancy can lead to malformations and abortion. Unfortunately, there is no effective therapy against chickenpox. Those affected must cure the viral disease. Bed rest, antipruritic agents and calf compresses in case of fever are the recommended measures. The best prevention against chickenpox is timely vaccination. The recommended age for vaccination is between 12 – 18 months. Vaccinated children and adults are up to 95 percent protected from infection because they develop sufficient antibodies. Chickenpox caused by the varicella-zoster virus is considered a first disease. After a long period of dormancy, the viruses can multiply again in the body in older people and due to a weakening of the immune system. This viral multiplication can trigger a secondary illness with shingles (herpes zoster). In most cases, this viral disease is visible as a strip-shaped skin rash in the middle of the body. In the process, a nerve becomes inflamed and spreads this inflammation to the surrounding skin tissue. Herpes zoster is an endogenous reactivation. Thus, it is not contagious and cannot be transmitted. It always develops only from a renewed activation of the varicella zoster viruses, which remain in the body even after infection with chickenpox. They settle in the nerve roots of the spinal cord and the ganglia of the cranial nerves. Herpes zoster is associated with severe pain. Also, the skin area from which the inflamed nerve is supplied burns. In the early stages, there may be mild fever and fatigue. Shingles develops in episodes. At first, painful elevations develop on the skin, which later turn into blisters. These blisters burst open after a few days and form a yellowish bark. After about two to three weeks, shingles heals. Scarring is common.Chronic courses with frequent blister formation may also occur. Shingles can be treated with antivirals. This is a substance that inhibits the reproduction of the viruses in the body. There are no drugs that directly destroy the virus. It is only possible to prevent it from spreading. Furthermore, it is common to administer strong painkillers for herpes zoster. If the patient had previously received a vaccination against chickenpox, the infection with shingles will be less intense. If professional treatment is given right in the first days of shingles, secondary diseases such as postzoster neuralgia can be avoided.
