An investigation into the epidemiology of tuberculosis in children: with special reference to the incidence among children known to have been in contact with a tuberculous person

The main objects of this investigation were grouped under two headings; A. Points of practical importance to the Tuberculosis Dispensary worker, and B. Objects concerning the Aetiology of Tuberculosis. It should be remembered that the statements which follow apply only to persons up to 22 years of ago.a. POINTS OF .PRACTICAL IMPORTANCE TO THE DISPENSARY WORKER. It was desired to obtain some information on the value of the von Pirquet reaction; to trace the course of disease, especially the more benign types, in those children found to be suffering from tuberculosis, and to evaluate the effect of treatment afforded by such a scheme as that to which the writer is attached; finally, to obtain some information on the life histories, subsequent to examination, of those who, at the time of examination, are written off the register as "Non-tuberculous", particularly to ascertain the incidence of tuberculosis, subsequent to examination, among contacts, with a view to deciding if periodical re- examination of all known contacts would be a profitable procedure.VON PIRQUET REACTIONS: Both the frequency and significance of positive reactions vary with age. They are commoner in contacts than in non-contacts but rather less frequently associated with disease in the former than in the latter.At least 75% of those suffering from tuberculosis will give a positive reaction. It is fair to regard the prognosis as bad in those with clinical evidence of tuberculosis but who give a negative reaction.During the first four years of life a positive reaction is a strong indication of the presence of active disease. From four to seven positive reactions become commoner but less significant. At about the seventh year there is a sudden fall in frequency, but both frequency and significance rise again slowly as puberty approaches, the results becoming more significant at a slightly earlier age in girls than in boys. About the fifteenth year, some 50. of those giving positive reactions show evidence of disease.INCIDENCE OF TUBERCULOSIS: Tuberculosis occurs more commonly in contacts than in the general population. If that portion of the latter which attends a tuberculosis dispensary be taken as an indication, it is commoner in females than in males. The adolescent type occurs at an earlier age in females than in males. The more benign typos of tuberculosis, such as disease of the hilum, of the mediastinal and cervical glands appear to be commoner in non -contacts than in contacts.The prognosis for those diagnosed as suffering from disease of the hilum and mediastinal glands appears good, but of course the possibility of error in diagnosis in these cases is probably greater than in any other type of lesion. In cases of disease of the cervical glands the outlook is much less favourable.The best results are obtained by institutional treatment. Those who attend the dispensary do better than those who do not.RE-EXAMINATION OF CONTACTS: Approximately 10% of those contacts who were written off the register as non-tuberculous subsequently developed tuberculosis (some of the others have not yet reached adolescence; including an estimated figure for these the percentage reaches 14). The average interval elapsing was 5 years. This is ample justification for the re- examination of all known contacts.b. OBJECTS CONCERNING THE AETIOLOGY OF TUBERCULOSIS: On page 3 are recorded some of the problems in the aetiology of tuberculosis on which it was hoped some light might be shed. These problems included such items as, •The relation between re-infection and immunity. •The normal duration of allergy. •The effect of re- infection during a period of (a) allergy (b) anergy, etc; •The effect of puberty on these states and the consequence of infection when they are so modified. It would indeed be rash to suggest that conclusive explanations of such problems can be made from the little information which has been obtained but the writer thinks that, on the evidence collected, the following comments are justifiable.Speaking graphically, the line of frequency of hypersensitiveness takes the form of a wave with a period which increases as age advances. Its maximum height is reached about the sixth year after which it falls suddenly. It is unlikely that children are less in contact with sources of infection during the seventh and eighth years than during the fifth and sixth and the writer suggests that about this age a period of anergy begins to succeed the period of allergy which followed previous infection.Towards puberty hypersensitiveness again begins to become a more common phenomenon. It is interesting to note that the more benign types of disease tend to occur in the middle period of childhood, that is about the period of suggested energy; while more serious varieties occur in the early years and again towards puberty, that is,to again make a graphic reference, on the rising segment of the allergic wave.Infection during the first four years is a serious matter. After the 4th year, infection seems to produce some degree of immunity, which, however, breaks down towards puberty. There is some suggestion that the immunity produced by repeated infection lasts somewhat longer than that obtained by casual infection. There is also some suggestion that those who are not infected during the first half of childhood are more likely to.infection with production of evident disease during the later years than those who have been previously infected