Chickenpox

Chicken pox was first described in the mid- 16th century by Italian doctors Vidus-Vidius and Ingranus as a variety of smallpox ^[4] .

The German scientist R. Vogel (1724–1774) first applied the term “varicella” (1772) and identified chickenpox as an independent nosological form ^[7] .

In 1911, the causative agent of chickenpox was found in the contents of the vesicles, after which the disease was considered a separate nosological form. The pathogen virus was isolated in 1958 ^[4] .

The epidemiology of chickenpox differs in temperate and tropical climates, the reasons for this are not clear. The differences are presumably the result of the properties of the virus - it is sensitive to temperature, climate, population density, and the risk of infection ^[5] .

The disease affects people of all ages. About half of the children are ill at the age of 5–9 years, less often - 1–4 and 10–14 years. About 10% of cases are 14 years old or older ^[4] .

The source of infection is a sick person from the end of the incubation period (10-21 days) until all lesions are covered with a crust (7-10 days). The causative agent is distributed by airborne droplets or by direct contact ^[5] . Contagiousness of chickenpox 100% - everyone who has not previously encountered the virus gets sick ^[4] .

Like all herpes viruses, chickenpox virus has the ability to suppress the immune system ^[8] .

Immunity with chickenpox causes resistance to a new infection, but does not ensure the removal of the virus from the body. The virus stays for life in the spinal ganglia and / or nuclei of the cranial nerves, which are associated with the areas of the skin that are most affected by the primary infection. Reactivation of the virus occurs under conditions of weakened immunity in the form of herpes zoster ^[8] .

Persons with severe immunodeficiency may re-infection ^[4] .

Shingles is a source of the virus and poses an epidemiological hazard in chickenpox ^[9]

The causative agent of chickenpox is the varicella zoster virus (Varicella Zoster), a large-sized virus visible in a normal light microscope , which has been detected in smallpox vesicles from day 3-4. The chickenpox virus is unstable in the environment - it quickly dies when exposed to sunlight, heat, and ultraviolet radiation . Outside the body, in the open, the virus survives about 10 minutes. The causative agent of chickenpox belongs to the viruses of the herpes group of the third type ^[10] .

Susceptibility to chickenpox is 70%. Patients with chickenpox become contagious 20-24 hours before the rash and remain up to 4 days.

The chickenpox virus infects only humans, the only reservoir of wild virus is humans ^[4] .

The varicella-zoster virus causes two diseases: chickenpox, which occurs mainly in childhood, and herpes zoster ( herpes zoster ), mainly affecting the elderly and people with immunodeficiency ^[4] . Chickenpox is the primary infection of varicella-zoster virus, and herpes zoster in the vast majority of cases is the result of activation of latent varicella-zoster virus ^{[4] [5]} .

The virus enters the body through the mucous membranes of the upper respiratory tract and invades the epithelial cells of the mucous membrane. Then the virus enters the blood and is fixed in the skin, causing a pathological process in its surface layer: limited expansion of capillaries (stain), serous edema ( papule ), exfoliation of the epidermis ( vesicle ).

Due to the multiplication of the virus and the allergic response of the body, fever and other common non-specific manifestations of the infection occur.

After the disease, persistent immunity occurs.

The causative agent may persist in the body; as a result of various provoking factors, it is activated and causes local skin rashes - herpes zoster .

During chickenpox, the following periods are distinguished: incubation , prodromal period , periods of rash and crusting.

• The incubation period for patients aged 30 years is 11-21 days, up to 30 years 13-17 days (average 14).
• The prodromal period occurs within 1-2 days before the rash begins (in some cases, the prodromal period is absent and the disease manifests itself by the appearance of a rash).

Prodromal phenomena in children may not be expressed. In adults, prodromal phenomena occur more often and are more severe (headache, lumbosacral pain, fever).

• The period of rash in most children proceeds without any special disturbances in the general condition, the febrile state coincides with the period of the mass appearance of the rash, the rash appears jerky, so the fever can be wave-like.

In adults, the rash is often massive, accompanied by fever, general toxic effects, severe itching.

The resulting rash has the appearance of pink spots of 2-4 mm in size, which within a few hours turn into papules, some of which, in turn, become vesicles. Vesicles are single-chamber, surrounded by a corolla of hyperemia . After 1-3 days, they dry out, forming superficial crusts of dark red or brown color, which fall off on the 2nd-3rd week. Since the rashes reappear, the rash is polymorphic in nature, that is, in a limited area you can see spots, papules, vesicles and crusts at the same time.

Along with skin rashes, enanthema appears on the mucous membranes. These are bubbles that quickly macerate , turning into a sore with a yellowish-gray bottom, surrounded by a red rim. More often the enanthema is limited to 1-3 elements. Enanthema heals within 1-2 days.

The febrile period lasts 2-5 days, sometimes up to 8-10 days (if the rashes are very plentiful and long). Rashes can last from 2 to 5 days, and up to 7-9 days.

Typically, chickenpox occurs benignly, but with the development of a bullous, hemorrhagic or gangrenous form of the disease, complications such as encephalitis , myocarditis , pyoderma , lymphadenitis are possible. The disease leads to death in 1 out of 60,000 cases ^[11] .

Chickenpox in a pregnant woman is not considered by doctors as an indication for artificial termination of pregnancy. If chickenpox is infected during pregnancy up to 14 weeks, the risk to the fetus is 0.4%, and if infected within 14 to 20 weeks, no more than 2%. After 20 weeks, there is virtually no risk for the child . Treatment with specific immunoglobulin during pregnancy dramatically reduces even this very small risk for the unborn baby.

However, with a woman’s disease 4–5 days before giving birth, a child with a 17% probability may develop congenital chickenpox, which is severe, accompanied by the development of extensive bronchopneumonia, diarrhea, perforation of the small intestine, and also damage to internal organs, and leads to death 31% of cases ^[12] .

Pregnant women are at risk of developing diseases associated with the Varicella Zoster virus. Intrauterine infection of the fetus during the first 20 weeks of pregnancy can lead to spontaneous abortion, fetal death, or the birth of a child with congenital chickenpox syndrome. Congenital chickenpox syndrome is characterized by malformations of the limbs, brain and organs of vision ^[9] .

There are no methods that would completely rid the body of this virus.

Treatment is carried out both on an outpatient basis (mild form) and in a hospital setting (in the presence of complications).

The principle of treatment involves the simultaneous solution of the following tasks: preventing the development of pathological processes and complications, preventing the formation of residual phenomena and disability.

When choosing a treatment technique, the following factors are taken into account: the clinical picture, the degree of manifestation of symptoms, the presence of complications, age, and other existing diseases in the patient.

Comprehensive treatment is the most effective and includes: regimen, diet, drug treatment, as well as non-drug treatment methods (room aeration , hygiene measures, physical temperature reduction) ^[13] . Bed rest should be observed during the entire febrile period ^[14] .

Local treatment at the lesion sites involves treating the skin and mucous membranes with a disinfectant solution to prevent bacterial infections ( Castellani solution , gentian violet, methylene blue , potassium permanganate solution ). Diamond green is not a mandatory treatment ^[15] . Synthetic tannins are used to dry the vesicles ^[16] , and external agents with allantoin and dexpanthenol are used to soften and heal the skin.

Paracetamol is widely used to lower the temperature. Ibuprofen is not recommended due to possible complications ^{[17] [18]} . Aspirin and its products should not be given to children with chickenpox (like any other illness causing fever), since there is a risk of severe and potentially fatal Ray syndrome ^[19] .

A direct antiviral effect was found in glycyrrhizic acid , which is used in local and systemic therapy. In moderate and severe forms of the disease, nucleosides and nucleotides are prescribed, in addition to reverse transcriptase inhibitors, for example, acyclovir ^{[19] [13]} . The use of antiviral agents is justified only for premature babies, patients with impaired immune systems and adults ^[4] .

The prognosis for chickenpox is usually favorable. It is recommended not to tear off the crusts in order to avoid residual marks.

Complications of chickenpox are rare and can be associated with the action of the virus itself or the layering of a bacterial infection. In this case, they start taking antibiotics. For infection of vesicles, bacitracin + neomycin (baneocin) is used ^[20] .

The chickenpox virus is prone to persistence, like the herpes simplex virus , and with weakening of the immune system (due to aging of the body, chemotherapy of malignant tumors, etc.), a relapse in the form of herpes zoster can occur (while the recurrence of chickenpox itself occurs very rarely).

The traditional "treatment" of chickenpox "green" is ineffective. More effective are baths with the addition of soda, antihistamines and painkillers ointments ^[4] .

A specific method of prevention is vaccination .

The vaccine was developed by Mitaki Takahashi in 1974 in Japan in the laboratories of the Bicken Foundation. The resulting vaccine strain was named Oka (in honor of a boy whose virus was isolated from the chickenpox vesicles). The first vaccine was called Okavax. Subsequently, Japanese developers transferred the Oka strain to the pharmaceutical companies Merck & Co and GlaxoSmithKline, which modified the strain and developed two more vaccines: Varivax and Varilrix.

In the USA, vaccination against chickenpox with the Varivax vaccine has been carried out since 1995, the vaccine is included in the national vaccination calendar. In the territory of the Russian Federation, the first vaccine for the prevention of chickenpox - Varillrix (GlaxoSmithKline Biologicals SA) was registered in 2008, and since 2009, vaccination has been widely used as part of regional immunization programs. In a number of European countries (eg, in the UK), vaccination is recommended only to people at risk ^[21] . In 2010, the original Japanese vaccine Okavax was registered in Russia.

The chickenpox vaccine is included in the national vaccination calendar of Australia ^[22] , Austria ^[23] , recommendations of the German Standing Committee for Vaccination ^[24] , and vaccination calendars of most Canadian provinces ^[25] . In the UK, the reluctance to introduce the chickenpox vaccine in the national calendar is motivated by fears that this may increase the risk of herpes zoster among older people, for whom contact with sick children is an immunity booster ^[26] .

The vaccine forms a stable immunity for many years. According to the experience of Japan, the first to use the vaccine, the patients immunity was preserved 20 years after vaccination, not a single vaccinated disease developed ^{[27] [4]} .

Vaccination is carried out according to the following scheme:

• Okavax vaccine: all persons under 12 months of age - 1 dose (0.5 ml) once
• Varilrix vaccine: for children over 12 months to 13 years old - twice with an interval of administration of 6-10 weeks (1 dose = 0.5 ml); children from 13 years old and adults - twice with an interval of administration of 6-10 weeks
• emergency prophylaxis (any of the vaccines): 1 dose (0.5 ml) during the first 96 hours after contact (preferably during the first 72 hours).

In case of illness, the person is usually isolated at home. Hospitalized patients living in dormitories, in specialized institutions or in large families. Also, serious forms of chickenpox, young children, in the presence of complications or other serious illness, are subject to hospitalization. Isolation stops 5 days after the last rash. For children attending organized children's groups, there is a procedure for admitting children to institutions provided for by the instruction. Disinfection due to the instability of the virus is not carried out, frequent ventilation and damp cleaning of the premises are sufficient.

Vaccine Effectiveness

The vaccination against chickenpox according to Taiwan was 82.6% ^[28] .

There is a risk of infection in the vaccinated patient - chickenpox breakthrough. The disease is possible both against the background of a decrease in post-vaccination immunity over time (the so-called "secondary vaccine deficiency"), and with primary tolerance, the inability of the body to induce an effective immune response. According to Taiwan's experience, a breakthrough of infection occurred in 2.1% of those vaccinated, and in 0.016%, hospitalization was required to treat the disease. The frequency of “chickenpox breakthrough” was the lower, the more children were vaccinated ^[28] .

Since chickenpox is more severe in adults than in children, some parents knowingly bring their children to a family with a chickenpox, calling it a “chickenpox party.” This practice was especially widespread before the chickenpox vaccine was introduced in the United States in 1995. Doctors say that it is safer for children to get a vaccine that contains a weakened form of the virus, rather than a disease that can be fatal ^[29] .

• Shingles
• Chickenpox virus

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