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47
of all males with positive sputum show previous important contact with the disease
in the intimate family circle, the percentage ranges from 21"6 and 23'8 per cent, in
the 16-20 and 21-25 year groups, respectively, down to 10'5 per cent, in those over
40 years of age. As age advances a similar diminution in the importance of contact
with a previous case is seen in females.
Females throughout, however, show a higher incidence of contact with previously
known cases. Thus, at all ages, 22 per cent, have been in important contact with
a previous case in the intimate family circle, while the percentage ranges from
31.4 per cent, in the 0.15 year group down to 17 per cent, in those over 40 years
of age.
The greater incidence of contact as a factor in the causation of the disease in
females, as compared with males, may be due to the wider opportunities of exposure
to infection in the family by reason of domestic and nursing duties. Kissing also
may be a factor.
As regards the relationship of what may be called the " infecting " case, it is
seen that the original cases were in parents in 20'6 per cent, in males, compared
with 27'5 per cent, in females. A tuberculous parent would seem to be a greater
danger to a daughter than to a son. Here again the reason may be the special
position of women in the household in regard to nursing and domestic duties and
the like.
During the last two years previous cases in parents have been subdivided
into the sexes and previous cases occurring in brothers and sisters have also been
separately recorded. Thus in 1,241 new male T.B. plus patients there was recorded
a previous case in 60 instances amongst brothers, and in 36 instances amongst sisters.
In 931 new female T.B. plus patients there was recorded a previous case in 50
instances among brothers and in 60 instances among sisters. It will be noted
that the sexes more frequently show contact with a previous case in the same sex
than in the opposite, and that this is more marked among males. Daily association
and proximity in sleeping probably account largely for this, the smaller diiference
in females possibly being due to their special position in the household as to nursing
and domestic duties with consequent increased risk of infection. Thus a daughter
in a household, while less in touch ordinarily with her brothers than with her sisters,
may have to help and come into close contact with a brother also, in the event
of sickness.
Similar considerations seem to hold good concerning previously known cases
occurring in the parents. In the 1,241 new male T.B. plus patients referred to above,
there were 41 instances of a previous case in a parent, and of these no less than
31 were cases among fathers. Turning to the 931 new female T.B. plus patients
in which this factor has been investigated, it is found that in 54 instances a parent
had previously been affected, and of these 28 instances were among fathers and
26 instances were among mothers.
Considering the clinical classification of the disease in the original case, it will
be seen from tables 56 and 57 that approximately three quarters of the " infecting "
cases are either living cases of pulmonary tuberculosis with positive sputum or cases
which have succumbed to pulmonary tuberculosis within the immediately preceding
five years.
Investigation has been made, in regard to the last two years' patients, into the
interval between the onset of a new patient suffering from positive sputum tuberculosis
and the death of a previous case of pulmonary tuberculosis within the
intimate family circle during the preceding five years. Data are available in
respect of 57 such instances among males. In 40 of these (70'2 per cent.) the
previous case in the family had died within the preceding two years. Among
females this information is available in 89 instances. In 48 (53.8 per cent.) the death
in the family had taken place within the preceding two years. The importance
of continued supervision of contacts (particularly for the first two years) following
the death in the family of a case of pulmonary tuberculosis is hereby demonstrated.