CHICKENPOX
(Varicella)
The Principles & Practice of Medicine (1958) Livingstone Ltd
Chickenpox is a viral infection which spreads by droplets from the upper respiratory tract or by contamination from the discharge from ruptured lesions of the skin. Occasionally the dermotropic virus of chickenpox becomes neurotropic and gives rise to herpes zoster. More commonly the neurotropic virus of herpes zoster produces chickenpox in persons who have been contacts. Chickenpox is highly infectious and chiefly affects children under 10 years of age. Most children are little incommoded by this disease but, as often happens with viral infections, adults may develop a more severe illness. Second attacks are very rare. The disease is not notifiable. The incubation period is commonly a fortnight. A quarantine period is not necessary.
Clinical Features. Constitutional symptoms are usually brief and mild, and the first sign of the disease is often the appearance of the rash. Lesions are sometimes present on the palate before the characteristic rash appears on the trunk on the second day of the illness. Then the face and finally the limbs are involved. The spots reach their maximum density upon the trunk, and are more sparse on the periphery of the limbs. The axillae should be inspected as this region is almost invariably affected, while in smallpox the reverse is true (Fig. 2). Macules appear first and within a few hours the lesions become papular and then vesicular. The vesicles are unilocular, very superficial, thin-walled and surrounded by a wide zone of erythema. The shape is elliptical rather than spherical. Within twenty-four hours the lesions become pustular. The vesicles and pustules are so fragile that they may be ruptured by the chafing of garments. Damage from scratching is also frequent, since itching may be troublesome. Whether or not the pustules rupture, they dry up in a few days to form scabs. The spots appear in crops, so that lesions at all stages of development are seen in any area at the same time. The course of the disease is usually uneventful.
Complications. Secondary infection of the lesions in the mouth and upon the skin by staphylococci and streptococci is the only common complication. Concomitant herpes zoster is unusual and encephalomyelitis may occur (p. 979). The latter is a rare complication of many virus infections.
Diagnosis. Although the typical case of chickenpox presents no diagnostic problem it is important to remember that great difficulty may be encountered in cases of modified smallpox and variola minor. When the skin rash has fully developed, however, the peripheral distribution of the lesions in smallpox is preserved. Serious consideration of the possibility of smallpox must be given to apparent cases of chickenpox occurring in patients who have just returned from an endemic area or at times when an outbreak of smallpox is known to be present. Typical variola major may be distinguished by certain features which contrast with those of chickenpox. In smallpox
(a) there is a prodromal illness of two to four days;
(b) the density of the lesions is greatest at the periphery, the rash is relatively profuse on convex and exposed surfaces, and the axillae are not affected (Fig. 2);
(c) the spots are deep-set, multilocular, circular lesions and are present predominantly at a single stage of development.
Treatment. Itching may be relieved by an antihistamine drug taken orally. No treatment is required in the majority of cases. At the first sign of secondary infection a dilute solution of potassium permanganate followed by a dusting powder should be applied to the skin. If bacterial infection progresses, penicillin should be given.
Spread of infection can be prevented by isolation of the patient and the sterilisation of all soiled articles, but the disease is so mild that in domiciliary practice these precautions are not usually taken.