What causes chickenpox

Varicella is a type of herpes zoster, a skin disease caused by a viral infection. That is why chickenpox spreads so quickly and can directly lead to systemic infection. This is because of the virus. The groups that are susceptible to infection are mostly children and infants, and they may even be infected during embryonic development. The transmission rate is very high, and there are many causes of the disease, most of which are related to environmental and population factors.

Causes :

Varicella-zoster virus infection :

Varicella-zoster virus and herpes simplex virus belong to the same herpesvirus subfamily. The virus remains latent in the host for a long time. When the disease occurs, it manifests as herpetic lesions on the whole body or local skin and mucous membranes. Its common feature is that it is easy to relapse. Varicella-zoster virus is a spherical virus particle with a diameter of about 150 to 200 nm and a double-layer lipoprotein envelope. There is only one serotype of varicella-zoster virus, and humans are the only natural host. Varicella-zoster virus VZV has weak resistance to the in vitro environment and quickly loses its activity in dry herpes scabs; but in herpes fluid, it can be stored at -65°C for a long time. The virus can be cultured in vitro using human embryonic fibroblasts, but cannot grow in general animal tissues such as chicken embryos.

Susceptible groups :

Generally susceptible, but preschool children are most likely to be infected. Infants under 6 months old are less likely to be infected because they obtain antibodies from their mothers. Chickenpox during pregnancy can infect the fetus, and the patient gains lasting immunity after the disease, but shingles may occur.

Source of infection :

Varicella patients are the main source of infection. The disease is contagious from 1 to 2 days before the rash appears until the rash dries and forms a crust. Susceptible children may also develop chickenpox when they come into contact with patients with shingles, but it is rare.

Pathogenesis

The virus invades the epithelial cells of the upper respiratory tract and replicates, then enters the bloodstream. After reaching the white blood cells, it replicates and then enters the bloodstream in large quantities to form viremia. The virus spreads to various organs and tissues throughout the body, causing systemic lesions. The skin lesions are mainly edema and degeneration of the spinous cell layer, and the nucleus divides into multinucleated giant cells with eosinophilic inclusion bodies formed in the nucleus. Subsequently, the cells liquefy and unilocular thin-walled blisters are formed. Early herpes fluid specimens can be observed under an electron microscope to contain a large amount of virus.