Varicella – colloquially known as chickenpox – (synonyms: chicken pox; varicellae; varicella; variola emphysematica [varicella]; variola hybrida [varicella]; variola illegitima [varicella]; variola notha [varicella]; variola spuria [varicella]; varicella (chickenpox); varicella; ICD-10 B01.-: Varicella [chickenpox]) is an infectious disease caused by the varicella virus (VCV; VZV), which is one of the childhood diseases. Varicella zoster virus (VZV) belongs to the Herpesviridae family, the Alphaherpesvirinae subfamily, and the Varicellovirus genus. In addition to chickenpox, the virus is also responsible for shingles (HZV; herpes zoster). Humans currently represent the only relevant pathogen reservoir. Occurrence: The infection occurs worldwide. The so-called contagiousness index (synonyms: contagiousness index; infection index) was introduced to quantify the contagiousness mathematically. It indicates the probability with which a non-immune person is infected after contact with a pathogen.The contagiousness index for chickenpox is close to 1.0, which means that close to 100 out of 100 unvaccinated persons are infected after contact with a person infected with chickenpox.Manifestation index: More than 90 % of those infected with chickenpox become recognizably ill with chickenpox. More than 95% of adults have antibodies to the virus. The virus remains in the body for life, which is why reactivations can lead to zoster, but these usually occur after the age of 50. Seasonal accumulation of the disease: Chickenpox occurs more frequently in winter and spring. Transmission occurs via droplets produced by coughing and sneezing and absorbed by the other person through the mucous membranes of the nose, mouth and possibly the eye (droplet infection) or aerogenically (through droplet nuclei (aerosols) containing the pathogen in the exhaled air) or through contact with the virus-containing vesicle contents and crusts. Transmission from mother to unborn child is relatively rare, but when it occurs, it can lead to the so-called fetal varicella syndrome. The incubation period (time from infection to onset of disease) is 8-28 days (usually 14-16 days). Frequency peak: The disease occurs predominantly between the 2nd and 6th year of life. 90% of all cases occur before the age of 20. A varicella-zoster virus seroprevalence (percentage of positive serological parameters (here: VZV) tested at a given time in a given population) of at least 96-97 % is assumed in Germany. The duration of infectivity (contagiousness) already exists one to two days before the appearance of the exanthema (skin rash) and ends approximately one week after the last efflorescences (skin symptoms) have subsided. Course and prognosis: In patients with a functioning immune system, the disease has no complications. The duration of the disease is 3-5 days. Severe courses occur in patients with atopic eczema (neurodermatitis), with T-cell deficiency (T-cells belong to the most important cell groups of the cellular immune defense) and in pregnant women. Varicella can lead to fetal varicella syndrome (FVS) in the first two trimesters (lat. : tri ‘three’ and mensis ‘month’ or trimestris ‘three months’) of pregnancy with a risk of about 1-2%. In high-risk patients, early antiviral therapy improves prognosis. In general, complications such as pneumonia, hepatitis, or meningoencephalitis (combined inflammation of the brain (encephalitis) and meninges) must be expected in adult infection. Vaccination: A vaccination against varicella is available. In Germany, direct or indirect detection of the pathogen is reportable by name according to the Infection Protection Act (IfSG), as far as the evidence points to an acute infection.
