EPIDEMIOLOGY OF TUBERCULOSIS—PARR 487 
are 10 clinical cases of tuberculosis for every annual death, we have in 
the United States less than 600,000 cases at the present time or only 
six times as many as now exist in little Belgium, which has perhaps 
only one-twentieth of our population. Many of our people are in, or 
shortly will be in, these unfortunate European countries. It would 
seem a safe prophecy to venture that the tuberculosis rate in this 
country may be slightly increased for a short period, but it should 
within a very few years again resume its downward trend. 
In view of the very low rate now obtaining (43.1 in 1942) it would 
be reasonable to expect a greater set-back relatively than we experi- 
enced at the end of World WarI. The magnitude of this set-back may 
not be so much one of significantly increased rate as of slowness to get 
under way again on the downward trend. For a disease as widely 
seeded in our population as tuberculosis and for a population more 
completely involved in abnormal war activity than was the case in 
World War I, it would not be surprising if this were to be so and the 
very favorable rates now attained would seem to be advanced posts 
we may have to abandon for some time. One factor in this slightly 
pessimistic prediction is our closeness to and commerce with the rest 
of the world in many parts of which tuberculosis is rampant. 
At one time the hope was expressed that we might be able to eradi- 
cate tuberculosis by a given date—say 1960. It should be understood 
that any such statement was merely a slogan, a cry behind which to 
rally the forces fighting the great white plague. As Frost ably 
pointed out in one of his last papers, entitled “How Much Control of 
Tuberculosis?” it “is not necessary that transmission be immediately 
and completely prevented. It is necessary only that the rate of trans- 
mission be held permanently below the level at which a given number 
of infection-spreading (i. e., open) cases succeed in establishing an 
equivalent number to carry on the succession. If, in successive periods 
of time, the number of infectious hosts is continuously reduced, the 
end result of this diminishing ratio, if continued long enough, must 
be the extermination of the tubercle bacillus.” I am not aware that 
Frost ever set any date for this millennium. As a very humble stu- 
dent of epidemiology I am sure I cannot. I doubt though if under 
present war conditions we have any reason to anticipate any lowering 
of the death rate for the entire country from 43.1 to even 10 per 100,000 
for several decades. Many millions of Americans are already tuber- 
culin positive; thousands of unrecognized advanced cases of tuber- 
culosis exist today; Europe and indeed most of the rest of the world 
is heavily tubercularized. It is too much to expect tuberculosis death 
rates to continue to drop as rapidly as they have in the past. To reduce 
194.4 by 10 percent is not so difficult as to reduce 43.1 by 10 percent. 
619830—45——32 
