Textbook of Medicine. E & S Livingston, Edinburgh 1945

Aetiology.—Chickenpox occurs all over the world, chiefly in localised epidemics in schools and children’s institutions. The disease is most prevalent in the winter months. Chickenpox and smallpox may be prevalent together. The virus is a filter passer distinct from that of smallpox or vaccinia. Amies has described elementary bodies similar to the Paschen bodies in smallpox. Though chiefly a disease of childhood, chickenpox attacks adults, and second attacks, though rare, are occasional1y seen.

Incubation Period.—From 14-21 days.

Clinical Description.—In children, the prodromal period may be absent or confined to slight pyrexia and increase in pulse-rate; adults, however, may exhibit prodromal symptoms such as malaise, nausea, and pain in the back for a period of twenty-four hours or, rarely, longer, before the eruption appears. There is occasionally a prodromal rash of scarlatiniform type. The lesions appear in from three to five crops over a period of two to four days. Initially macules or maculo-papules, they become, within a few hours, clear, well-filled superficial vesicles, many of a typically elliptical shape. In twenty-four hours the vesicles assume a pale yellowish opalescent appearance and become flaccid pustules. Ultimately, scabbing and separation take place. Shallow, pinkish depressions which form white cicatrices are left. Owing to the fact that the lesions appear in crops and that the cycle of the individual lesions from papule to scab is a short one, lesions in various stages of development are present upon the skin after the first twenty-four to thirtysix hours. The eruption probably always first appears within the buccal cavity, but the lesions here are so delicate that they readily rupture and may not be recognisable. They may occur within the larynx and upon the conjunctiva. Upon the skin they first appear upon the back, chest, and abdomen— particularly the lower abdomen—and the adductor aspects of the thighs. The face and hairy scalp are next invaded. The arms and legs, including sometimes the palms and soles, are usually the last to present lesions.

The distribution as a whole is centripetal, being most abundant upon the trunk. The numbers of lesions upon the upper arms exceed those upon the forearms; the numbers upon the thighs those upon the legs. The lesions of chickenpox, in contrast to smallpox, tend to invade concavities and protected surfaces such as the axilla.

Herpes and Varicella.—The virus of chickenpox, ordinarily dermatotropic, occasionally assumes neurotropic properties resulting in the clinical manifestations of herpes zoster. This is not to say that herpes zoster is invariably due to the virus of chickenpox.

The exceptional occurrence of encephalitis provides further evidence of the neurotropic affinities of the virus.

Complications.—The occasional occurrence of vesicles within the larynx has been noted. Very rarely this localisation has necessitated tracheotomy. Lesions upon the conjunctiva, being quite superficial, rarely give rise to trouble. In debilitated children the lesions may ulcerate or become gangrenous. Varicella gangrenosa may be caused by the infection of the lesions with haemolytic streptococci or virulent diphtheria bacilli, giving rise to early fulminating and late subacute forms respectively. Diphtheria and scarlet fever antitoxins and sulphonamides should be given as soon as possible in all cases of V. gangrenosa.

Diagnosis.—If the points noted under clinical description are carefully compared with the description of smallpox, confusion between the diagnosis of the two diseases should not arise. The prodromal scarlatiniform rash is sometimes diagnosed as scarlet fever. Papular urticaria, the lesions of which never appear in the mouth, scabies, and impetigo have also to be excluded.

Treatment.—Bed and light diet for a few days are desirable. It is important to prevent undue scarring, either as the result of scratching the lesions or of secondary impetigo. Small doses of the sulphonamides, given early in the attack, may reduce the severity of pustulation. Separation of the scabs is facilitated by treating each with carbolised oil applied gently with a feather.

Mode of Spread and Prevention.—The disease is most infective in its earliest stages. Infectivity wanes rapidly after the full appearance of the eruption, but isolation should be maintained until all the scabs have separated. Infection is commonly conveyed from person to person; in the early stages the virus is readily carried upon the hands of a third person who has been in attendance. There is some evidence that in its early and most infective phase chickenpox may be spread for short distances, as from bed to bed, through the air. Prevention consists in the earliest possible isolation of cases, concurrent and terminal disinfection, and an observation period of 21 days for exposed non-immune children.

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