OCCURRENCE; MODE OF SPREADING; AGE INCIDENCE Varicella is a disease which occurs among all races and which never disappears entirely from the larger cities. Large and small epidemics are of frequent occurrence and are most often seen about the time of the opening of the schools. Nearly all the epidemics are of a benign character but exceptionally there may be numerous cases of nephritis, secondary infections, or gangrene. Unusually wide spread epidemics have occurred, however, in which the disease resembles variola in its course, the epidemic described by Mombert occurring in Kurhessen in 1S 2-I may be cited as an example.
Varicella is almost exclusively a disease of childhood and some authors, Senator for example, have gone so far as to speak of an immunity in adults, and have given this as a point in differential diagnosis. Others state that the disease is of such exceptional occurrence in adults that all cases occurring in grown people should be under the supervision of the sanitary authorities. On this account adult patients with varicella have been sent to smallpox hospitals and have there contracted variola. During the past year there have been such a large number of cases in grown people in places which were previously and have remained free from smallpox that the question of the occurrence of chicken-pox in later life may be regarded as settled.
However this may be, every case of chicken-pox in an adult should be gone into carefully to avoid the possibilities of error. It is especially important to remember that a variola-like exanthem is common in the varicella of adults. Doubtful cases should be handled in the same way as smallpox owing to the probability of its being that disease and the danger of spreading the contagion if it should be.
The incubation period is relatively long. In the majority of the cases the eruption appears on the fourteenth day after the infection, sometimes on the thirteenth and more rarely as late as the seventeenth or even the nineteenth day and in some cases the incubation period is given as four weeks.
As a rule the prodromes are unimportant or absent. Thomas and Henoch say that in most cases the eruption is the first symptom and, in fact, one often hears from the most anxious and observant mothers that nothing was noted until the appearance of the eruption. Bohn, Gerhardt, Cerf and many French authors are of the opinion that mild prodromes are the rule. Semtschenke found this to be the case in SOS cases out of 872 but his observations were made in a Russian orphan asylum where hygienic conditions were not of the best.
The prodromal symptoms last only one or two days, rarely four or five, and consist of fever, anorexia, restless sleep, general malaise, and sometimes there is pain in the abdomen, vomiting and nose bleed. Pain in the joints and back may be so intense as to suggest variola. High fever is noted in children who usually have high temperature from slight causes and severe nervous symptoms may he met with in some cases. Demme has noted blood in the stools which disappeared with the eruption.
The length and severity of the prodromes varies and it must be noted that a patient who has had severe prodromes may have a very favorable and short course of the disease.
In typical cases the eruption appears on the scalp and face and nearly at the same time over the body. There are numerous small round spots part of which either remain small or disappear altogether,. the remainder enlarge and form papules about the size of a pea. A small vesicle forms on these in the course of a few hours and this may increase greatly in size. The eruption may be seen in all stages on the same patient at the same time. The picture suggests an astronomical map where irregular stars of various sizes are situated close together (Heubner). After a day or less the contents of the vesicles begins to be absorbed and in a couple of days there remains only a yellow brown or black scab. This drops off in a few days usually without, leaving any scar.