ChickenPox (Varicella): Health Significance To Man, Pathology, epidemiology And Clinical Presentations

Chickenpox is a common viral infection occurring frequently in children. The disease is highly contagious. It is characterized by fever and disseminated vesicular eruptions. Though, in children,t he disease is benign and self-limiting as age advances the disease becomes more serious and produces grave compliations.

Varicella virus, the etiological agents of varicella and herpes zoster are identical in all respects. The varicella zoster (V-Z) virus is a DNA virus measuring 100 to 150 nm in diameter. It multiplies in the nuclei of infected cells and produces intranuclear inclusions.

Pathology: The patient is most infective towards the end of the incubation period and early part of the disease. Virus is present in the discharges from the upper respiratory tract in the early stages. The portal of entry is the respiratory tract. The epidermis undergoes degeneration and vesicles containing serum, polymorphs and multinucleated giant cells are formed. Virus is present in the vesicle fluid for 3 to 4 days, but not in the crusting lesions or scabs.

As a complication, pneumonia may occur. In varicella pneumonia, the tracheobronchial mucosa, the alveolar septa and the interstitial tissues of the lungs are edematous and show mononuclear cells with intranuclear inclusions and giant cells. Pneumonia develops as nodular areas of consolidation in the lungs. Ultimately, these lesions may become calcified. Encephalomyelitis which resembles that seen in measles may occur as a complication. During the acute phase of the disease infants and children may develop acute encephalopathy with fatty infiltration of the viscera (Reye’s syndrome).

Epidemiology: The infectious period extends from a day or two before the onset of the rash of six days after the appearance of new skin lesions or until all vesicles have started crusting. Chickenpox develops commonly due to exposure to other cases of chickenpox and rarely in contacts of Herpes zoster. Herpes zoster is mainly a disease of adults who have partial immunity to the virus. Though chickenpox produces good immunity, it wanes off after 10 years and second attacks may develop.

The rashes appear 14 to 16 days after exposure (range 10 to 23 days). Prodromal symptoms are mild in children, the first manifestation in whom is the appearance of vesicles, Early symptoms in adults include fever, headache, backache, sore throat and malaise which last for 2 or 3 days. Enathema occurs over the palatal and pharyngeal mucosa even before the skin rash appears. The skin rashes (exanthema) come up in crops starting from the first day of fever and these continue for 3 to 4 days so that lesions at different stages- may be present simultaneously (polymorphism). The rashes are centripetal, maximally affecting the trunk and sparing the distal parts of the limbs. Face may be affected variably. The axillae are almost invariably affected. The vesicles are unilocular, superficial, elliptical in shape and contain clear fluid in the beginning (teardrop vesicles). These become pustular in 24 hours. Intense prurutus may develop and scratching disrupts these vesicles. The pustules dry up to form scabs in a few days. When the scabs fall off, superficial scars are left behind which clear up in due course. Recovery is the rule in the vast majority of healthy subjects. Complications and death may occur in immunosuppressed persons and children receiving adrenal steroids.