DISTRIBUTION OF MALARIA 
17 
South, malaria mortality is relatively low, 
although the morbidity may be appreciable. 
These inferences are in accord with the 
evidence that the benign malaria parasite, 
P. vivax, is the only known autochthonous 
species in this territory. In the Southern 
United States, malaria appears to be spread¬ 
ing radially from three or four highly en¬ 
demic foci. Although the mortality rate 
in the South as a whole has reached a rela¬ 
tively satisfactory low level, certain foci 
have a maintained tropical malaria death 
rate. While there is a wide range in ma¬ 
laria mortality rates reported from Mexico, 
Central America and the West Indies, the 
average for these countries as a whole is at 
least 20 times that of the Southern United 
States. 
4. There are adequate laboratory facili¬ 
ties for the accurate diagnosis of malaria 
films in several of the United States and in 
a few of the tropical countries surveyed, 
but diagnosis is still too commonly based on 
clinical evidence and therapeutic tests. 
Moreover, diagnosis of malaria plasmodia 
in the blood of clinic patients provides no 
real evidence of the prevalence of the infec¬ 
tion in the population as a whole. Thus, 
most official records of malaria morbidity 
are unreliable as an index of the amount of 
malaria and of the relative incidence of the 
different species of malaria plasmodia in a 
given area. 
5. Extensive blood film examinations of 
representative cross sections of the popula¬ 
tion constitute the most accurate basis for 
determining the malaria index of a coun¬ 
try. Surveys of this type have been carried 
out or are in progress in some of the United 
States and in several of the other countries 
under consideration. 
6. While splenic enlargement is proba¬ 
bly not as accurate an index of malaria as 
is blood film examination, spleen surveys 
carried out on children are fairly reliable 
and offer an opportunity for determining 
malaria incidence in areas where facilities 
and training are inadequate for diagnosis 
of the parasites in blood films. 
7. Throughout the territory favorable for 
the propagation of all three common species 
of human malaria plasmodia, the relative 
incidence of P. vivax and P. falciparum 
varies, but for any leirge area P. malariae 
is relatively unimportant. 
8. In all of the warm areas surveyed P. 
falciparum is the species primarily responsi¬ 
ble for malaria deaths. 
Acknowledgment 
Sincere thanks and appreciation are ex¬ 
tended to the many persons who have pro¬ 
vided the basic data from which this report 
has been compiled: to all officials in the 
bureaus of vital statistics of the depart¬ 
ments of health of each of the United 
States, to Dr. J. J. Heagerty, Director of 
Public Health Services, the Dominion of 
Canada and to Professor Thomas W. M. 
Cameron, McGill University, for informa¬ 
tion on malaria in Canada; to Dr. Jorge 
Rendon Gomez of the Federal Department 
of Public Health and to Professor Carlos 
C. Hoffman, Instituto de Biologia, for 
Mexico; to Dr. Carlos Estevez, Director 
General of Public Health, for Guatemala; 
to Dr. Vernon F. Anderson, Acting Senior 
Medical Officer, for British Honduras; to 
Dr. Pedro H. Ordonez Diaz, Director Gen¬ 
eral of Public Health, for Honduras; to 
Colonel Luis Manuel Debayle, Medical Di¬ 
rector General of Health, for Nicaragua; 
to Dr. A. Pena Chavarria, Secretary of Pub¬ 
lic Health, and to Dr. H. W. Kumm, Inter¬ 
national Health Division, Rockefeller Foun¬ 
dation, for Costa Rica; to Lieutenant- 
Colonel James S. Simmons, M. C., United 
States Army, for Panama; to Dr. Laureano 
Lopez Garrido, Office of the Secretary of 
Health and Welfare, Professor Pedro 
Kouri, University of Habana, and Dr. 
Henry P. Carr, International Health Divi¬ 
sion, Rockefeller Foundation, for Cuba; to 
the Director of Medical Services, for Ja¬ 
maica; to Dr. Rulx Leon, Undersecretary 
of State for Hygiene, Public and Social 
Welfare, for Haiti; to Dr. Luis Francisco 
Thomen, for Republica Dominicana; to Dr. 
E. Garrido Morales, Commissioner of 
Health, for Puerto Rico; to Dr. Meredith 
Hoskins, Chief Municipal Physician, De- 
