INFLAMMATORY DISEASES OF THE RESPIRATORY TRACT (BRONCHITIS, INFLUENZA, BRONCHOPNEUMONIA, LOBAR PNEUMONIA)<sup>a</sup>
<sup>PART I
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http://history.amedd.army.mil/booksdocs/wwi/communicablediseases/chapter2.1.htm#table14<sup>PART I
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In approaching the consideration of the serious and fatal inflammations of the respiratory tract which formed by far the most important factor in the sickness and death records of the Army during the World War, it is first necessary to take a general view of the subject in the attempt to determine, if possible, the causes that led to the large morbidity and mortality from respiratory diseases in general, rather than to limit ourselves to the consideration of each form of disease separately.The mortality from respiratory diseases during the World War was due almost entirely to pneumonia, primary or secondary.<sup>1</sup> In any set of communities the size of the mobilization camps of the Army during the war, pneumonia is to be expected to some extent. The usual type of pneumonia occurring among young male adults in civil life is of course primary lobar pneumonia, running a fairly definite course and, usually, recognized easily both clinically and post mortem.
That such cases occurred among the troops is beyond question. The proportion of such cases, however, is impossible to determine. McCallum expressed the opinion, after studying the pneumonias at Camp Travis, Tex., in the late winter of 1917-18, that they were relatively few in number and distinguished mainly by their mildness as compared to those seen in civil communities.<sup>2</sup><sup> </sup>
However, it was early recognized clinically that in the larger number of cases observed in the camps the pneumonia was of an atypical nature. The onset tended to be slower than that of the lobar pneumonia of civil life; the course more prolonged. Crisis was relatively rare; physical signs were slow of development and of patchy distribution and scattered in several lobes. These facts led careful observers to consider a large proportion of the cases as bronchopneumonia rather than as the usual lobar type. The results of post-mortem study of fatal cases lent confirmation to this distinction: The typical croupous consolidation of lobar pneumonia was relatively rare, patchy consolidation of a suppurative character more frequent.
Even when the consolidation involved nearly or quite an entire lobe, careful study often showed evidence of the formation of such lobar consolidation by the confluence of smaller areas, lobular in origin.
Inasmuch as bronchopneumonia is almost invariably a complicating or secondary, rather than a primary infection, and its incidence in men of military age, generally speaking, is very low as compared to that of the lobar type, attention was at once focused on the coincident epidemic of measles as the probable primary cause of the pneumonias.
That this disease was indeed a large factor in the causation of the pneumonias of the early days of the mobilization camps of the World War is shown in the consideration of that disease.
<sup>a</sup>Unless otherwise stated, all figures for the World War period are derived from sick and wounded reports sent to the Surgeon General.?Ed.
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However, in many, if not in most camps, the peak of the pneumonia incidence did not coincide with that of the measles and in the light of subsequent events attention is directed to the possible occurrence in the camps at this time of another disease also complicated by fatal pneumonia, namely, influenza.
It will be shown that influenza, at least in its so-called endemic form, was a considerable factor in the sick rates of the Army for some years before the World War.
It has always been held responsible for a small but varying mortality in the civil population according to the reports of the Census Bureau. It is the consensus of opinion of those who have investigated the subject that minor but distinct epidemic waves of this disease have occurred every few years, in each instance accompanied by an increase in the pneumonia mortality.
Cases of influenza were reported from the camps from the earliest days of the mobilization; doubtless many more cases were not recognized owing to the mildness of the type prevailing during the fall of 1917.
It is impossible, therefore, to estimate the number of influenza cases that occurred among the troops during these early months. But that the disease was present will be shown in a manner that will leave very little room for doubt, and its fluctuations from month to month, as shown by its effect on the number of admissions for the total respiratory diseases and by its effect on the amount and character of the prevalent pneumonia, can be shown with some definiteness.
Unfortunately for the exactness of our records in this class of diseases the clinical characteristics of mild influenza are such as to lead to its ready confusion with several of the milder so-called common respiratory diseases.
Of these, bronchitis, tonsillitis, and pharyngitis are the leading diseases with which many of the earlier cases of influenza were confused.
When the outbreak was at its height the uniformity of symptoms presented by large numbers of cases made confusion almost impossible and at the time of an epidemic wave in the majority of instances the cases were correctly diagnosed.
However, in certain camps there were pathological purists who refused to give sanction to the diagnosis of influenza unless it was possible to demonstrate the presence of the bacillus of Pfeiffer.
This attitude was evidently extreme, in view of the doubt cast in recent years on the specificity of the r?le of this organism in influenza; but the fact remains that in all of the epidemic waves to be described, even in the generally recognized fall outbreak of 1918, there was not only an increase in the number of cases diagnosed as influenza but also a corresponding increase in the "other respiratory diseases."
One camp reported a preponderant number of influenza cases, another simultaneously suffering from the same epidemic wave reported few influenza cases, but a great increase in the common respiratory diseases.
Even in the 1918 fall wave, three camps?Fremont, Calif.; Gordon, Ga.; and Wheeler, Ga.<sup>3</sup>?apparently insisted on a bacteriological diagnosis, which was not forthcoming, and reported their epidemic cases as "other respiratory diseases." These two factors then, the impossibility of making an exact clinical diagnosis of influenza in the absence of the great outbreak, and the insistence by some on the bacteriological diagnosis even in the presence of undoubted waves of the disease, make it impracticable to base conclusions as to the varying incidence of influenza in the Army camps on the reported cases of that disease alone. In studying the varying incidence of influenza, therefore,
<hr noshade="noshade" size="1">it becomes necessary to use not only the figures for that disease as reported, but also those for certain other acute respiratory infections. In using this combined figure we are undoubtedly including a certain number of noninfluenzal cases.
In view of the number of cases involved, however, and of the more or less constant incidence of these diseases as usually observed, it is believed that the use of this figure will give the most reliable comparative index of the month-to-month incidence of influenza that it is possible to obtain.
The study of the relations between the incidence of the common respiratory diseases and of the pneumonias, therefore, should serve to throw light both on the causation of the high pneumonia incidence and mortality as well as on the character of the responsible primary infection. For this reason, it seems impossible to consider separately the epidemiology of the pneumonias and of influenza.
It should be understood in studying the various charts presented that the system of recording admissions for disease in use in the Army during the World War referred each case back to date of admission. Thus, if a man was admitted with measles during one month and his complicating pneumonia did not develop until the following month, the pneumonia would be reported as occurring in the former month, the date of the original admission. This simplifies the reading of the graphs as, for instance, the peak of measles admission and of the complicating pneumonias will thus appear in the same month.
No allowance is necessary for the lapse of time between the development of the primary disease and the onset of the complication.
As to the accuracy and completeness of the figures used in the following pages, it must be said that doubtless many cases of pneumonia escaped record in the monthly tables used, by reason of the fact that the disease of record was taken to be the one given as the cause of the original admission.
Complications and intercurrent diseases were included in the tables of concurrent diseases, solely for enlisted men in the United States and Europe, and when complicating disease, not injury, but were not classified by months, except to some extent those occurring in influenza, and in measles.
However, for the present study the figures are very satisfactory and while doubtless many pneumonia cases were recorded under some other heading this error was undoubtedly a nearly constant one and the important facts, the fluctuations in the rates from month to month, are believed to be shown with substantial accuracy.
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