EPIDEMIOLOGY OF TUBERCULOSIS—PARR 479 
course, occur in a child provided it is an individual who has had “first 
infection phase” tuberculosis. It was formerly thought that such dis- 
ease arose chiefly from one’s own reservoir of tubercle bacilli held over 
from an arrested “first infection phase” attack. The fact that over- 
work, worry, undernourishment, and other untoward socioeconomic 
factors predispose to tuberculosis fitted in very well with the idea that 
each man carried about his own potential tuberculosis and might light 
it up as an adult by lowering his personal resistance. 
The following quotation from the American Review of Tuberculosis 
(Dobbie, 1920) is not the point of view held today: 
In adults the problem of preventing infection requires very little attention. 
The great majority of adults have already been infected before reaching adult 
life. What adults have to fear most is not further infection from without, but an 
extension of the infection which they already have, leading to the development 
of a group of Symptoms which we are pleased to call the disease tuberculosis. All 
adults should of course avoid prolonged and intimate contact with the grossly 
careless tuberculous person ; but there is little to be feared through ordinary con- 
tact. It has been said that the careful consumptive is not a danger to anyone. 
This might be modified to read the consumptive is a grave menace to infants, less 
dangerous to children, and no danger at all to adults if reasonable care be 
exercised. 
Let me emphasize again. We should not be afraid of the tubercle bacillus. For 
ourselves, as adults, as a rule we need fear no attack except from those that are 
now in our bodies. For the children, since we cannot permanently protect them 
from invasion, let us wisely choose the time when the bacilli are first to be met. 
If this be done, the tubercle bacilli may be transformed from a menacing enemy 
into a protecting friend. This is what should be taught to every adult, as com- 
prising the knowledge in accordance with which he should live and act as an 
individual. 
Today we favor the view that tuberculosis may be contracted from 
continued contact with open cases and that its incidence may be 
reduced by eliminating sources of infection from milk or meat; by 
minimizing contact with open cases through early and accurate diag- 
nosis and isolation; and by proper care of those having tuberculosis 
including full attention to proper nutrition and conditions of living. 
What a change of point of view within a generation! Some areas are 
even working on the hypothesis that all tuberculosis can be prevented. 
Certainly one cannot develop tuberculosis without first becoming 
tuberculin positive. Hence, in certain parts of the country where 
conditions are favorable an effort is being made to place tuberculosis 
on the county accreditation basis. In 1940 the death rate for tubercu- 
losis in the continental United States was 45.9 per 100,000, one of the 
finest rates anywhere in the world. It is a reasonable estimate that in 
that year about 50 percent of our total population were tuberculin 
positive. Minnesota has established county accreditation for tubercu- 
losis. This “new idea in human tuberculosis control” provides that a 
