Chickenpox (varicella) – Causes, Symptoms, Diagnosis and Treatment

Chickenpox (varicella) is an acute infectious disease, universally prevalent and mainly effects children below 10 years of age though older children and young adult,s are also effected.

An acute attack of the disease is characterized by fever and a rash which appears in crops. It is highly contagious and in most cases it is self limiting. One attack of chickenpox usually affords complete protection from future attacks.

Etiologic agent

Chickenpox is caused by varicella virus which is closely related to herpes simplex virus, cytomegalovirus and epstein bar virus (EBV). It is a DNA virus and multiplies in the nuclei.

The major sources of virus are discharges from the respiratory tract and skin lesion. Virus enters the respiratory passages by droplet infection and when patient scratches the skin lesions it becomes aerosolized. Although respiratory tract remains an important source of conveying the virus yet it is difficult to culture the virus from respiratory secretions.

chickenpox (varicella)

Incubation period

It is between 10 to 21 days. The spread of disease is air borne and person to person contact. The infectious period is one to two days before the appearance of the rash and lasts till all the skin lesions have crusted which is usually 5- 7 days.

Clinical picture

Chickenpox (varicella) consists of a stage of invasion or prodromal stage and stage of eruption.

Stage of invasion: The prodromal symptoms are mild and consist of fever, headache backache, malaise and sore throat. This stage usually lasts for 2-3 days. Child is irritable and restless. This is followed by the appearance of eruption which is generally taken to be the first day of the disease.

Stage of eruption

The eruption of chickenpox (varicella) first appears on the back and then spreads to the other parts of body like face, scalp, chest, abdomen and lastly the proximal part of limbs. The rash appears in the form of crops at first macular then papular, vesicular and becomes pustular in 24 hours. Distribution of rash is centripetal maximally affecting face, trunk and limbs from above and sparing the distal part of extremities.

Appearance of crops of rash after a lapse of a day or two may produce skin lesions in various stages of development at the same time. Pruritis is intense and often leads to rupture of the vesicles. Vesicles present on the mucous membranes may rupture leaving behind shallow grey ulcers.

Rashes generally last for 3-4 days and after that are followed by the formation of scabs which fall off in a few days leaving behind superficial scars. Complete clearance of skin may take few days.


Generally chickenpox is a mild disease but sometimes variable form of the disease may be seen. There are three varieties:

1. Varicella bullosa characterized by formation of bullous eruptions.

2. Varicella gangrenosa: It is seen in ill nourished children and there are dark crusts formed in the eruptions which on separation leave behind ulcers.

3. Varicella haemorrhagica: It is uncommon but a very virulent form. Hemorrhages occur into the vesicles and bleeding may take place from mucous membranes.

Complications in chickenpox (varicella)

Generally the extent of rash is a good indication of mildness or severity of the disease. In patients with serious illness the number and extent of skin lesions is massive. Various forms of complications include respiratory (laryngitis bronchitis, bronchopneumonia) skin (secondary infection with staphylococci or haemolytic streptococci may produce erysipelas, impetigo) kidney (nephritis) and arthritis.

Neurological involvement is not common but may be in the form of encephalomyelitis, ataxia, transverse myelitis and optic neuritis. Myocarditis, purpura and keratitis are some of the other complications.

Since herpes zoster is closely related to varicella, a scattered rash simulating chickenpox may precede or accompany an attack of herpes zoster though the reverse in cases of chickenpox is not common.


Clinical picture of a case of chickenpox (varicella) is very typical. A child presenting with a rash with its typical distribution and coming in crops and presenting with macule, papules, vesicles pustules and scabs at the same time is quite diagnostic.

In cases of doubt diagnosis is confirmed by staining of skin scrapings with fluorescein labelled monoclonal antibody and the diagnosis is made within a few hours. Skin lesions can also be cultured for the presence of vims.


Since chickenpox (varicella) is a contagious disease the patient should be isolated till every scale has separated. In the majority of cases only symptomatic treatment is required. Child should be confined to bed especially in the stage when rash is developing.

Analgesics like Paracetamol syrup teaspoonful thrice a day is given to relieve pain and fever. Many times the child is irritable. In such case phenergan syrup 1 teaspoonful twice a day is advised. It shall also relieve pruritis.

In immuno-compromised patients and those either with serious complications or virulent form of the disease antiviral drug Acyclovir (20 mg/kg body weight) in four divided doses is given for five days. Secondary infection should be treated with broad spectrum antibiotics.

Prophylaxis. It is always advisable to isolate children with chickenpox (varicella) and care should be taken to protect the contacts.

Passive immunization is produced by use of varicella zoster immune globulin (VZIG) in a dose of 0.5-1 ml/kg body weight within 72 hours of exposure.

Live attenuated varicella vaccine (varivax) in a dose of 0.5 ml is administered in all children above the age of 12 months for immunization. It induces nuclei mediated immunity and protects against or significantly reduces the morbidity associated with primary VZV infections. A booster dose after six years of vaccination is also given in some children.

Prognosis. A case of chickenpox has a self limiting course and in an uncomplicated case prognosis is good.

Quick Look

1. Incubation period 10-21 days

2. Etiologic agent Varicella virus

3. Clinical picture Stage of invasion or prodromal stage

• Stage of eruption

• Convalescence

4. Complications

Respiratory- Laryngitis, bronchitis,


Skin- Erysipelas, cellulitis, impetigo

Renal- Nephritis

Systemic- Arthritis, encephalo myelitis, myocarditis, purpura

In majority of patients having chickenpox (varicella), this is a mild stage but in debilitated children, adults and immuno-compromised person it is a fulminating course.

Before the appearance of skin rash, enanthem develops over the palatal, buccal and pharyngeal mucosa.

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