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108
2.—Infection in childhood is much less dangerous than in
infancy as only about 40 to 60% of those infected are found to be
suffering from tuberculosis.
3.—In adolescence, the general health is liable to be undermined
by social, physiological and economic changes. Fresh infection
is dangerous and the types of disease that develop are serious.
Among contacts it has been found that tuberculosis is commoner
in females than in maids. Contacts remaining healthy
during childhood show a high incidence of the disease during
adolescence, therefore, contact examinations to be effective must
include the "following up" of contacts during adolescence, especially
after leaving school.
About 90% of children up to the age of 18 years in the large
towns in Europe and America are infected, as shown by the tuberculin
test. Prom this fact it is clear that there must always be in
the community a considerable number of persons with latent tuberculosis,
such persons are potentially infective and are at any time
liable to develop manifest disease. The actual extent and site of
the lesion in latent tuberculosis can be ascertained only by X-ray
examination, and it is for this reason that in certain parts of Canada
and the United States all contacts are tuberculin tested and if
found to be infected are examined radiologically as a routine
measure, such examination has shown that, more than 10% of
school children have latent tubercular foci in the lungs and adjacent
glands.
Careful watching of these children, with preventive treatment
where necessary, should result in a considerable diminution in the
number of cases of active tuberculosis among young adolescents.
Elsewhere in this report it will be seen that there is an increase in
the morbidity and mortality from pulmonary tuberculosis in young
adults. In girls of 15 to 20 the mortality from! pulmonary tuberculosis
is greater than from tuberculosis from all causes in the
infant.
No recognised method of protection against tuberculosis has
been evolved either by tuberculin or living bacilli. The reported
success of experiments with B.C.G. still awaits confirmation. The
policy that appeals most is to prevent infection or to dilute it as
far as possible. Where this has been done by sanitation cleanliness,
correction of overcrowding, and protection of the milk supply,
tuberculosis has decreased. There is no evidence that any success
has followed attempts to diminish the incidence of the disease by
artificially endeavouring to produce immunity, and in some cases