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The Section on Epidemiology

Excerpts on the Influenza and Pneumonia Pandemic of 1918


This section was placed in the division of infectious diseases and laboratories on November 1, 1918. Before that time it had existed as the section on communicable diseases of the division on sanitation.

The work of the section consisted in the study of disease conditions in the Army and the recommendation of measures for their better control. These investigations were carried on by means of epidemiologists located in the camps and by the help of a large number of reports from camp surgeons, sanitary inspectors, and in fact all officers charged with the duty of observing sanitary conditions and reporting the same to the Surgeon General. It was intended that all reports which dealt with communicable disease should pass through the section on epidemiology.

The scope of the studies was world wide. Not only was the progress of disease in the camps in America kept under observation, but through the cooperation of the United States Census Bureau, the Military Intelligence Division of the Army, the Public Health Service, and the Department of State, information was focused in this section concerning the appearance of epidemic diseases in the environments of United States troops in America, France, Siberia, and other parts of the world.


The information which was received by the section was recorded in the form of tables, abstracts, memoranda, spot maps, and diagrams. By these means it was possible at short notice not only to tell what information had been received on a given subject, but to compare the present conditions with conditions which had existed at previous periods and at different points during the war. The studies of the section went still further in the direction of research. Records as far back as reliable data existed were collected, tabulated, and analyzed in order the better to understand the progress which had been made in the Army in the control of infection and the difficulties which had to be overcome in order to make further progress.

The work of the section found expression in (a) periodic reports in which the disease conditions of the Army were critically reviewed, (b) special reports which dealt with particular and unusual disease conditions as they occurred, (e) numerous memoranda recommending action, and (d) many formal reports in which the subjects dealt with were broadly and maturely considered.

A considerable part of the work of the section was concerned with the analysis of the records of disease which was sent to the Surgeon General's Office each week by telegram. These, compiled in the form of tables, were called current statistics. Much importance attached to these records, and it was the opinion of the section that the system employed should, with certain modifications, be established as a permanent institution in the Army in the United States; heretofore it has been for expeditionary forces only. The value of the current statistics lay in their immediate availability. It was not indispensable that they should possess great accuracy, but it was a matter essential that the information should come promptly to the Surgeon General's Office. The telegraphic reports, which furnished the basis of the current statistics, could, in any case of necessity, be readily verified.

Among the researches carried on by the section, in order the better to comprehend Army infections and how they could be more perfectly controlled, were the following:

A study of disease conditions in the Army for 23 years, as indicated in the annual reports of the Surgeon General, and in many scientific papers and monographs, showed (1) that the type of the leading infections has changed from the enteric to the respiratory group, (2) that a gradual lowering of the admission and death rates had occurred, except at various periods of unusual military activity, and (3) there was need of concentrating attention upon the respiratory group of infections.

In order to better understand the changes in the prevalence of disease which had occurred in the Army investigations were made of the vital statistics of many cities and States. Some of the records were followed back for many years; in this work the resources of the Surgeon General's library was of much assistance. It was found that most of the infectious diseases had everywhere, greatly declined within the last generation or so with the exception of pneumonia.

The influenza pandemic occupied a large share of the attention throughout the section's existence. Various lines of investigation concerning it were carried on; one sought to obtain from the camps and other station troops, records of more than ordinary accuracy regarding the number of cases and deaths and the detailed measures


of control which had been employed, as well as the opinions of epidemiologists and others, concerning the efficiency of the suppressive measures. Another line of investigation sought to analyze the individual camp epidemics and to figure them graphically in order to discover such underlying principles of infection and restraint as might thus be brought to light. It was found that the epidemic curve was typical of influenza and that the disease, as it existed in the Army camps, assumed various aspects, according to the geographical position of the camp and other factors. The epidemic curves of the camps were compared with the epidemic curves of upward of two score large cities, with the result that the influenza epidemics in the camps were found to be far more explosive than those in civil life. The difference was accounted for, partly upon the score of the age of the exposed persons, and partly by reason of the greater opportunities which were afforded in the camps for the transmission of the virus. When allowance was made for the age distribution, the epidemic curves for the cities more closely resembled the curves for the camps.

A feature of the work of the section was the use of diagrams and other graphic means of handling the great mass of data which came to the section for assimilation. The diagrams were of three principal types; one was interested simply to illustrate facts already known and which needed to be set forth in a striking manner; the second was intended to bring to light facts which would otherwise be hidden in tables of numerical figures; the third group consisted of analytical curves, the object of which was to discover conditions which could not be revealed by any other means. In all of , this work simplicity, directness, and practical utility were continuously aimed at.

The methods employed by the Army for the control of disease were constantly under critical study by the section, the intention being to discover such need of improvement as the conditions of warfare revealed, and to meet these needs as promptly as better methods could be devised. Particular attention was given to the practical aspects of the subject, it being remembered that ideal conditions could not be accomplished among troops composed of untrained recruits hastily brought together for rapid, intensive training.

Many facts and opinions of more than temporary value, which were arrived at by the section, were published by members of the section in current medical journals, and it is to those reports that the reader must be referred for detailed information.