—from Epidemiological Bulletin, Vol. 21 No. 3, September 2000—

Epidemiology in Latin America

Initially published in the Spanish edition of the Bulletin of the Pan American Sanitary Bureau, Vol. LI, No.3, September 1961. Presented by Dr. Abraham Horwitz during the Symposium on World Medicine at Yale University in New Haven, CT, 17 March 1961.

According to Paul (1), 4,000 years had to pass before epidemiology became an independent discipline, and in 1920 it was finally in a position to appear as such among the arts and medical sciences. However, the concepts and principles on which modern epidemiology is based are essentially the same as those established by the most distinguished founders of this science.

Today the analytical reasoning of Snow, Panum, Goldberger, and Frost - to mention only a few significant figures in this field - is still being applied for the purpose of reaching a better understanding of the sick or healthy human being; and in our opinion, it should be applied even more to gain an accurate knowledge of humans as social beings.

By 1878, Hirsch (2) had already described historical and geographical pathology as the “science that…, in the first place, will present a general table of the frequency, the distribution and classes of diseases of humankind, in different times and in several points of the surface of the Earth; and secondly, will state the relation that exists between those diseases and the external environmental conditions that surround individuals and determine their lifestyle.”

This description can be accepted as a definition of modern epidemiology, since as Frost (3) rightfully pointed out, it implies that epidemiology is essentially an inductive science, a science that not only deals with the distribution of diseases, but also frames, perhaps to a greater degree, that distribution within a consistent doctrine.

However epidemiology, like all the sciences in which assumptions play a part, can be defined in various ways. This multiplicity of definitions reflects the wealth of materials that it studies, since it encompasses all the factors related to human life regardless of its origin. Whatever definition we choose, the science of epidemiology, in its current concept, encompasses all the human interactions with their extended and immediate environment, both in a healthy and sick state. In this regard, the word epidemiology is synonymous with medical ecology.

Thus, it includes and facilitates the interpretation of life. And because the principles on which it is based have remained constant, the only variation comes from the circumstances in which diseases occur or do not occur, spread or do not spread; that is, from the changes in and the adaptation to the environment, which is the characteristic of all living things.

I would like to mention the opportunities for epidemiological studies that today’s new world offers, especially in Latin America. We Latin Americans like to describe the Americas - with respect to the distribution of diseases - as a continent in transition, where the main quarantinable diseases are disappearing. There has not been one single case of cholera registered since the beginning of the century. In 1960, 250 cases of plague, the majority of jungle origin, were reported; there were 650 reported cases of typhus transmitted through lice, some 50 cases of jungle yellow fever, and smallpox did not reach 5,000 cases. It is true that the incidences of other communicable and diarrheal diseases are higher than they should, but chronic diseases are already becoming important causes of death in most Latin American countries. Cancers, cardiovascular diseases, and accidents appear today among the 10 leading causes of death in these countries. At the same time, we are registering an increase in life expectancy, a growing industrialization and a fast urbanization. But contrasting with these fast social changes, which influence health problems and at the same time are influenced by them, is the fastest registered population growth in the world, widespread illiteracy, a per capita income that ranges between 100 and 500 dollars per year, the drawback of countries depending on export of a single product, insufficient investments, and the unavoidable consequences of all this, that is poverty and misery.

The solution to many health problems in the Americas will be found using epidemiological processes. Given the geographical variations of the diseases, there is not a field in which epidemiology does not have an important role to play. I wish to mention, as examples, some of the issues for which the Pan American Sanitary Bureau, Regional Office of the World Health Organization, is promoting fundamental epidemiological studies.

As long as no comparable mortality data are available, there cannot be progress in the epidemiological study of diseases in the Region. The evaluation of the quality of a death certificate, which Morris (4) calls “Operational Research”, is a matter of general interest. In the Americas, we will study this problem in depth, recognizing in the first place, that the quality of death certificates has to be improved greatly and that it hinders the comparison of mortality statistics. We plan to prepare comparable data of selected cities, through the acquisition of a complete clinical history and the anatomico-pathological elements of each death; medical death certificates will be completed and systematically coded in accordance with international procedures. As a first step, researchers in ten or more medical schools will establish centers in which medical statisticians, epidemiologists, and pathologists will work jointly to provide the essential data for epidemiological studies. Once the distribution of mortality is known with accuracy - through death rates, by age groups, corresponding to specific diseases -, the investigators will begin exploring the factors causing the encountered differences. This type of coordinated research will make it possible to convert certain selected medical schools into practical research centers and thus provide high-quality training in epidemiology. The establishment of these centers, preferably in departments of preventive medicine, to train a new generation of epidemiologists, can have an enormous impact on the medical sciences. The National Institutes of Hygiene (USA) have just provided a grant to hold a conference for the purpose of planning these epidemiological studies in the Region of the Americas.

In the field of cardiovascular diseases, research is under way at the regional level to throw light upon the natural history of the atherosclerotic injuries observed in population groups that live in different environments and have genetic backgrounds that vary considerably. Histopathological laboratories in eleven countries, among them the United States and others of Central and South America, are sending specimens of aortas and coronary arteries obtained from necropsies to a central laboratory, to be examined for the purpose of determining the variations that are observed in the atherosclerotic lesions by age, weight, race, geography, nutritional status and disease. This authentically Inter-American project is being carried out by the Institute of Nutrition of Central America and Panama, under the auspices of the National Institutes of Hygiene of the Public Health Services of the United States of America and with cooperation of the School of Medicine of the University of the State of Louisiana. To date, more than 2,500 aortas and coronary arteries have been examined.

As malaria is yielding in the Americas under the impact of vast eradication programs, new epidemiological problems are beginning to arise, and problems that are in the process of disappearing, such as malaria, require new and intensive research. The fact that areas of stable transmission of malaria can now be delimited is, in itself, a manifestation of progress, but their existence despite well-executed interventions forces us to conduct new epidemiological research.

The persistence of malaria transmission in certain areas requires new research on the problems of behavior change in the rest habits of the anopheles, the transmission outside of residences, asymptomatic carriers, and the daytime transmission by certain vectors. The resistance of the anopheles to insecticides and of the plasmodia to drugs, as well as the genetic variations in the susceptibility to toxic substances are among the problems which we should face. It is also necessary to conduct studies for the evaluation of medicated salt programs and to determine with more precision the therapeutic effect of antimalarial drugs with respect to different strains of plasmodia. It is necessary to determine the role of migrating workers, nomadic and hard-to-reach populations, in the complex problem of malaria eradication.

Studies conducted in the Institute of Nutrition of Central America and Panama have demonstrated that there exists a synergistic relationship between malnutrition and infections such as diarrheal diseases, whooping cough and measles, a combination that causes death in children under 5 in many Latin American countries. This relation seems fragmented and circumstantial, and it is necessary to conduct adequate epidemiological studies to determine both its scope and its implications for preventive programs. INCAP is investigating this problem in three localities of Guatemala. In the first locality, a program is being developed to reduce infectious diseases by means of preventive measures, treatment and improvement of sanitation. In the second location, special attention is given to nutrition, and for this purpose milk and other protein-rich food is being distributed, while at the same time a nutrition education program is carried out. The third locality serves as control. It is expected that the findings of this research will make an important contribution to our current knowledge.

With respect to the practice of public health, I wish to underline the imperative need to conduct epidemiological research on the subject of medical care, especially in those Latin American countries in which these activities are financed mainly with social security funds. The same should be said about the evaluation of health services needs for the planning of long-term programs. Diseases caused by virus, mental disorders, alcoholism, the dangers of radiation and atmospheric pollution also offer enormous possibilities for research to determine their effects on morbidity and mortality in the various countries. Comparative epidemiological studies would represent a valuable contribution for an in-depth knowledge of the cause and origin of the diseases.

I am totally in agreement with Dr. Morris (4), with regard to Latin America, when he states that “epidemiology is today the Cinderella of medical sciences” and that “it is necessary to say that public health needs more epidemiological studies, to the level of medicine in general, and even society as a whole.”

As for the teaching of medicine, I do not believe that it is unfair to say that the concept of epidemiology is not receiving sufficient attention in the education of physicians and public health workers. Apparently, the predominant element in medical teaching continues to be the diagnosis and treatment of diseases. Due attention is not given to medicine as a social science, nor to the study of man as a biological and social entity, with the consequent result that, in medical studies, the analysis of the impact of health and disease on society is merely incidental and does not leave its mark on the student. Consequently, students do not form a conception of medicine as a science that brings together disease prevention, the treatment of patients and health promotion. The fulfillment of the responsibilities that they will assume in modern society will depend more on their intuition than on the knowledge that they have of the epidemiology of diseases in relation to the community.

In the field of public health, epidemiology has often been regarded as synonymous with communicable disease control. The practice and enforcement of knowledge have eclipsed the analysis and the making of assumptions. Epidemiology has been emphasized as a purely descriptive science. Frequently, we do without it in the analysis of common problems of any origin that affect the family, the group or the community. And it is with even less frequency regarded as an indispensable method for studying the operation of health services. The need is more obvious than ever for introducing into medical teaching a better and broader concept of epidemiology, and for duly preparing epidemiologists with a broad vision of the possibilities that science offers them. In this regard, international health organizations have a concrete function, of great importance, to return the true significance to the meaning of epidemiology, as the art of thinking well and interpreting life.

References:
(1) Paul, J.R.: Clinical Epidemiology, University of Chicago Press, Chicago, Ill., United States, 1958.
(2) Hirsch, A.C.: Handbook of Geographical and Historical Pathology, New Sydenham Society, London, 1883-1886.
(3) Frost, W.H.: Papers of Wade Hampton Frost, The Commonwealth Fund, New York, 1941.
(4) Morris, J.W.: Uses of Epidemiology, E and S Livingstone Ltd., Edinburgh and London, 1957.

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Epidemiological Bulletin , Vol. 21 No. 3, September 2000