THE ANTI-MALARIA PROGRAM IN NORTH AMERICA 
367 
1914 through 1940. The heavy line illus¬ 
trates the cyclic waves of malaria. As the 
rate declines the area of infection shrinks. 
During the sudden subsequent rise there is 
an increase in severity of the disease, the 
appearance of epidemics, and a re-invasion 
of the territory which may have been free 
of infection for a number of years. The 
distinct decline to its low points in 1932 
and 1940 is the result of drainage, larvicide 
application, screening, better housing, and 
control of impounded waters. During each 
half decade of declining rates it is probable 
that mass immunity falls, thus leaving a 
population ready for subsequent peaks.. 
The steady decline between 1914 and 1932 
probably allowed this immunity to reach 
its lowest ebb and may be the reason for 
the prompt rise during the summers of 
1934 and 1935. The intensity of malaria 
has steadily fallen since the peak of 1935 
and is still falling. The next peak is due 
during the summer of 1941 or 1942. 
Apparently the cycle in our tropics is of 
shorter duration. It is approximately two 
years in the Chagres River Valley of 
Panama (Clark et al. 1940). When the 
cycle is worked out in all our other repub¬ 
lics, their health administrations could be 
prepared for epidemic peaks and could 
attack them as the British have done in the 
Punjab, though the British predict their 
epidemics not on periodic occurrence, but 
from the previous flood season (Gill 1938b). 
Foci of infection should be located and as 
many as possible eliminated through anoph- 
eline control during the periods of falling 
rates; treatment facilities should be pro¬ 
vided for epidemic control, when the cycle 
is due for a peak. 
In our tropical countries morbidity and 
mortality records of malaria are incom¬ 
plete and inaccurate, so an estimate of the 
number of infections is impossible. In the 
United States mortality records are of some 
value. In a few states morbidity records 
are accurate enough to indicate relative 
intensities. From the deaths and known 
cases in the United States, and from an 
index of 130,000 school children (Williams 
1935) it is estimated that the number of 
infections annually varies from one to six 
million; the average is believed to be four 
million cases (Williams 1938). 
Although it has been frequently stated 
that the infection is widespread, it is not 
possible to calculate the cost of malaria in 
Central America or the West Indies. Such 
estimates of cost have been made for the 
United States; first, in 1917 the annual loss 
in southern industry and agriculture was 
considered by H. R. Carter (1919) to be 
over $100,000,000 annually and 20 years 
later (1937) the yearly cost of sickness was 
estimated by Williams (1938) to be about 
$51,000,000 and the economic loss at $500,- 
000,000. Bearing in mind the high cost of 
malaria, the expenditure by governments 
of millions for control seems reasonable. 
Nevertheless active suppressive measures 
did not commence in the United States 
until 1912 and did not become a recognized 
part of State health work until about the 
time of the first World War. Its growth 
was slow as the cost of drainage seemed 
high to the people living in infected terri¬ 
tory. The extended use of oil and screen¬ 
ing and the introduction of Paris green 
reduced the cost so that some control mea¬ 
sures at last became possible for nearly all 
people. 
The program for control in the United 
States received a great stimulation during 
the time of the first World War in con¬ 
nection with extra-cantonment sanitation. 
During this emergency period the Govern¬ 
ment financed some rural work for camp 
protection which was so expensive that the 
localities, unaided, would not have at¬ 
tempted it. It drew attention to the neces¬ 
sity for expanding the research program 
to find cheaper methods. In addition to 
stimulating research, the War work brought 
about the development of some form of 
malarial control units in each of the south¬ 
ern states and gave a great impetus to the 
formation of county health units through 
which control could be further extended. 
More recently the Relief Administration, 
during the depression, created malaria con¬ 
trol projects to give employment to hun¬ 
dreds of thousands of men. Under this 
