The initial prodromal phase of varicella consists of malaise and low grade fever. Fever is rarely above 102 F. The characteristic feature of varicella is the formation of cutaneous vesicles. Exanthem develops over 3 to 6 days. Usually it begins along the hairline on the face as red macules that progress to tiny vesicles with surrounding erythema. It is often described as “dew drops on a rose petal”. The vesicles then form pustules which become crusted and scabbed over. The rash appears in successive crops over the trunk and then the extremities. In the first week, there are lesions in different stages of development. By the end of the first week, the fever subsides and the cutaneous lesions start crusting, become dry and fall off. Eventually they heal leaving no scar behind.

Complications of varicella include the following:

• Bacterial infection: Bacterial infection of a vesicular lesion is the most frequent complication of varicella. Common bacteria infecting the vesicles include group A streptococci and staphylococci. Less common but more serious bacterial infections are toxic shock syndrome, sepsis, cellulitis, erysipelas, cutaneous abscesses, impetigo and suppurative lymphadenitis. 
• Viral sequelae: Viral sequelae of varicella may involve all systems. Most common are pneumonitis, hepatitis, arthritis, pericarditis, glomerulonephritis, orchitis and involvement of the central nervous system (such as encephalitis).
• Purpura fulminans: Purpura fulminans is a large ecchymosis that appears on the legs. Occasionally, it may progress to hemorrhagic gangrene. 

The diagnosis of varicella is usually made on clinical grounds on the basis of the characteristic vesicular rash. The following investigations may be helpful in establishing the diagnosis if clinical examination is not sufficient.

• Blood count: White blood cells are usually normal or low. Increase in the number of white blood cells suggests secondary bacterial infection. 
• Chest X-ray: In case of varicella pneumonitis, numerous bilateral nodular opacities may be seen in X-rays of the chest. Hyperinflation may also be apparent.
• Viral sampling and cell culture: Varicella zoster virus may be identified by obtaining samples of the fluid in the vesicles and for inoculation in cell culture.
• Immunological tests: The most reliable methods for testing varicella zoster humoral immunity are fluorescent antibody to membrane antigen (FAMA) and enzyme linked immunosorbent assay (ELISA) [3]. 

In a healthy child, varicella is not a serious disease. The treatment of varicella consists of the following components.

• Maintenance of hydration: It is important to maintain hydration in the children suffering from varicella.
• Good hygiene: General good hygiene should be maintained by keeping the nails trimmed and keeping the skin clean. This reduces itching and the likelihood of damaging the skin due to sharp nails.
• Antipyretics: Paracetamol is the antipyretic used to control the low grade fever of paracetamol. Aspirin should be avoided to avoid the risk of Reye’s syndrome.
• Calamine lotion: Calamine lotion may be applied on the skin to relieve the severe itching associated with varicella. 
• Diphenhydramine syrup: In case of uncontrolled itching and discomfort, diphenhydramine syrup may be given to provide adequate relief.
• Antibiotics: In case of secondary infection of the skin, antibiotic therapy is necessitated. 
• Varicella zoster immunoglobulin (VZIG): Varicella zoster immunoglobulin (VSIG) may be given in the children who are immunocompromised or who are receiving corticosteroid therapy for any other condition [4] [5].
• Acyclovir: In case of varicella infection, there is no beneficial effect of varicella zoster immunoglobulin after 4th day post-exposure. In such cases, acyclovir is given for 7 days in a total daily dose of 1500 mg per square meter of surface area. Intravenous acyclovir blocks further viral replication within 24 to 48 hours. Such early treatment prevents the development of progressive varicella and its associated complications [6] [7].

Varicella is not a very serious disease and therefore, the prognosis is usually good. The mortality depends upon the health and the age of the child. The mortality rate of children suffering from varicella is around 1 in 50,000 children. In infants, the mortality is much higher at 1 in 13,000 children. Children on high dose steroid therapy have a greater risk of developing complications of varicella. Mortality from varicella has declined in the United States since the implementation of vaccination [2].

Varicella is caused by one of the human herpes viruses; specifically varicella zoster virus (VZV). Varicella zoster virus is a DNA virus and is transmitted by droplets in respiratory secretions. Air currents from an infected child to a susceptible child carry these water droplets. Varicella is contagious from 24 to 48 hours before the rash appears and while uncrusted vesicles are present – which is around 3 to 7 days.

Varicella is a common disease of children. It occurs equally in all races and genders [1].

After a susceptible child receives the virus, there is an incubation period of around 10 to 20 days before the appearance of the characteristic vesicular rash. The initial site of infection is the conjunctivae or the upper respiratory tract. The virus then replicates for about 4 to 6 days at a local site in the head or neck. Thereafter, the virus is transmitted throughout the body which is known as primary viremia. One week later, the virus is released in large amounts after a second replication. This is known as secondary viremia. The virus then leaves the capillaries and invades the epidermis of the skin. The characteristic vesicles of varicella then appear on the skin.

Varicella can be prevented by the use of varicella vaccine [8]. Varicella vaccine is not recommended below the age of 1 year. After the age of one year, a single dose of 0.5 ml is recommended. Herpes zoster may also be prevented in adults by the use of varicella vaccine [9] [10]. Infection with varicella confers lifelong immunity in the host.

Varicella, more commonly known as chicken pox, is a common exanthem of the pediatric population. It is caused by varicella zoster virus. The salient features of varicella are malaise, rash, fever and headache. After recovery from the initial infection, the virus still remains in a latent state within the dorsal root (sensory) ganglion cells. In around 10 to 15% of the cases, the virus may reactivate in old age when the immune system becomes weak. In such cases, there is a characteristic exanthem in a dermatomel pattern which is referred to as herpes zoster or shingles.

Varicella is a common infectious disease of children and is known as chicken pox. It is caused by a virus and is characterized by the formation of rash. It is not a serious disease but prompt treatment is necessary to prevent the development of complications.

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