Related resource: Influenza-Related Medical Terms

Chapter II
Inflammatory Diseases of The Respiratory Tract
(Bronchitis, Influenza, Bronchopneumonia, Lobar Pneumonia)^a

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 of secondary.¹ 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 morten. 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.² 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.

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^a Unless other wise stated, all figures for the World War period are derived from sick and wounded reports sent to the Surgeon General.--ed.

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, ash 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, tonsilitis, 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 rôle 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.³--apparently insisted on a bacterial 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,

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 qare 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 csausation of the high pneumonia incidence and mortailty as well as on the character of the responsible primary infectiojn. For this reason, it seems impossible to consider separately the epidemiology of the pneumonias and of influencza.

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 r4eferred each case back to date of admission. Thus, if a man was admitted with measles during one month and his complicating peneumonia 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 developoment 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,m 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 prsent 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.

Epidemiology

The history of epidemic infleunza dates back to the dark ages of medicine and much of its is involved in the obscurity of uncertain diagnosis. It is outside the sphere of this chapter to consider this even in the most cursory manner. Suffice it to say that the records of periodic visitations of epidemic acute respiratory disease of such character as to be reasonably supposed to have been influenza go back almost as far as does written history. These outbreaks have been of varying character and the descriptions sometimes lead to doubt as to the influenzal character of the disease. Some outbreaks were associated with large numbers of fatal cases of pneumonia while others equally widespread were accompanied by relatively slight fatality. Before the pandemic of 1918 the

latest general outbreak of the disease was that of 1889-90,⁴ involving very large numbers of cases, but, compared to the more recent outbreak, a small loss of life. Even in this outbreak the fatality of the various waves varied greatly. Since that pandemic several minor outbreaks of less general distribution have occurred, notably in the winter of 1907-08⁴ and in that of 1915-16.⁵ Neither of these led to enough excess mortality to make any considerable impression on the mortality curves althbough it is evident on careful study.

The mortailty figures for the United States registration area, 1911-1920,⁶ show a regularly varying curveds for deaths from influenza and from the pneumonias, highest during the winter months, although at times the highest point was reached in March. (Chart V.) The highest monthly rates for influenza prior to 1918 were reached in the winter of 1915-16, and were accompnaied by some increase in the pneumopnia death rates. This increased death rate for pneumonia continued with slight remission during the succeeding years up to the great pandemic of 1918, after which the death rates for incluenza for the whole area dropped back to normal. It was noted, however, that certain cities, New Orleans for example, showed an even higher death rate for influenza in the winter of 1917-18 than had been the case two years earlier. There appears to have been then a certain possible increase in the prevalence of influenza and to a greater extent of pneumonia in the few years preceding the great outbreak of 1918.

Chart V.--Comparative trends of mortality rates per 1,000 for pneumonia and influenza, United States registration area for deaths, 1911-1920.

For the Army, statistics are available since 1840, except for the period of the Mexican War. There is little evidence in the records of any exceptional prevalence of influenza during the Civil War.

From the end of the Civil War to the beginning of the World War there was an almost uninterrupted slow decline in the admission rates for pneumonia in the Army.⁷ This was broken only by two considerable elevations, one in 1888, the year before the outbreak of 1889-90 unfluenza pandemic, and a second, almost as high, coinciding with the mobilization for the Spanish-American War in 1898, from 1913 there has been a very slight tendency for the rates to rise. The figures for influenza are less satisfactory owing to the confusion as

to the exact diagnosis of the condition. Following the Civil War relativley low rates prevailed for a few years to be succeeded by a period of some 15 years when the reported rate ran nearly as high as that reached during 1890, when the peak of the pandemic reached the Army. Immediately preceding the pandemic, however, several years were recorded with as low a rate as was the case later. Following the 1889-90 pandemic the rates gradually descended; low points were reached in 1902 and in 1914. The case fatality of the pneumonis was high during the Civil War and again reached almost the same point in 1918. The high point in the intervening years was reached in 1887, after which time there was a tendency to a gradual decline. In 1904, 1907, and 1915, all yeyars in which influenza was noted as more than usually prevalent in the civil population, there is a simultaneous rise. In the years previous to the 1889-90 pandemic there appears to be no easily traceable relation between them. With the exceptions of these relations, shown both in the civil and military statictics between the incidence and the mortality for influenza and pneumonia, it would appear that the really significant fact brought out by these figures is that there is present at all times even in the interepidemic periods a diseqases of such a character clinically as to lead large numbers of physicians, both in the Army and in civil practice, to call it influenza. Whether this disease is the same as that occurring in epidemic outbreaks remains for the future to decide, and the decision will be made when etiologic studies have progressed to the point that will render it possible to make a diagnosis based on the identity of the inciting agent.

Prevalence and Importance During the War Period

General tables for the period of the war have been prepared showing the total number of admissions and deaths from influenza, bronchitis, bronchopneumonia, and lobar pneumonia in the various racial groups comprising the Army, and for the different countries in which our troops were stationed. Rates have also been calculated for each of these groups based on a strength which was obtained by the addition of th emean annual strengths for each of the years of the war. The resulting rate is an average of the annual rates weighted for the variations of strength from year to year. The figures thus obtained possess decided comparative value; they show the results that may be expected from different races and in the different climates over a considerable period of time in the presence of epidemic outbreaks of influenza. On the other hand, they are open to the objection that applies to all single figures purporting to represent averages--the details are inevitably obscured. for the detailed study of the epidemiology of these conditions the rates by months for the different groups are vastly preferable. These monthly rates are given in the study of the effect of race and length of service on the incidence and the mortality of the diseases unde4r consideration. The consideration of these general tables, however, will serve to give an outline of the respiratory disease sitaution in the Army during the World War, and certain general conclusions may be drawn from them as to the relative prevalence and fatality of these diseases in the different groups.

Table 10.--Respiratory diseases. Primary admissions, officer and enlisted men, United States Army, by countires, April 1, 1917, to December 31, 1919. Absolute numbers and annual ratios per 1,000 strength.

Table 10 shows the absolute number of primary admissions for racial groups and for totals. Thus it is seen that influenza, bronchitis, bronchopneumonia and lobar pneumonia were responsible for 1,125,401 primary admissons in the entire Army. Of these, influenza is credited with 791,907 admissions; bronchitis, 255,148; bronchopneumonia, 32,572; lobar pneumonia, 45,774. These diseases occurred also concurrently with, or secondarily to, other diseases or surgical conditions for which patients primarily were admitted to hospital, and were, in many instances, probably responsible for much of the mortality which occurred and was otherwise reported. It is not now possible to discover the total number of instances in which influenza, bronchitis, bronchopneumonia, and lobar pneumonia occurred concurrently with other diseases or as complications of surgical conditions; however, partial results are possible. Thus, it is possible to account for 798,509 cases of influenza, 279,597 of bronchitis, 96,495 of bronchopneumonia, and 76,147 of lobar pneumonia. Allowing for the instances were diseases of this group complicated other diseases of the same group, it is possible to account for 797,993 cases of influenza, 272,735 of bronchitis, 37,334 of bronchopneumonia, and 51,115 of lobar pneumonia, a total of 1,159,177 cases of respiratory disease; which, as stated above, can be only an approximation.

There were in all, during the World War, 3,515,464 admissions to sick report for disease. Of these, 32 per cent were primarily for respiratory disease, while an additional 0.96 per cent of the total suffered from these diseases secondarily. The comparison of the annual ratios per thousand also is shown in Table 10. The total mean annual strength of the Army for the years 1917-1919 was 4,128,479.⁸ It can be said, then, that 18.33 per cent, or 1 man to every 5.17, contracted influenza in the service, 6.27 per cent, or 1 to every 15.14, contracted bronchitis, 0.86 per cent, or 1 to 110.58, contracted b ronchopneumonia, and 0.17 per cent, or 1 to 80.77, contracted lobar pneumonia. The 1,159,177 cases of respiratory diseases represent 26.63 per cent of the total number of men in the Army, or 1 to every 3.5 men. Venereal disease was responsible for the next largest number of admissions (357,969), followed by mumps with 230,356 primary admissions and acute tonsillitis with 176,408.

As to group incidence, theh figures show that the incidence was in general higher among the American enlisted men (276.01) than among officers (205.89). The highest admission rates shown by any group was for the enlisted men from Porto Rico. Of their total rate of 455.04 per 1,000 for respiratory diseases, however, 37.51 was for influenza. Their primary admissions for the pneumonias, especially for bronchopneumonia (2.45), were relativley low. The next highest admission rate was shown by the colored enlisted men in the United States (422.41). The colored rates were consistently higher than those for the whites under the same conditions except for the colored enlisted men in Hawaii, who had the lowest rate for total respiratory disease (104.22) shown by group. The rate for the enlisted men of the Philippine Scoutes (191.23) was lower than that of the Army as a whole (272.60), while that for the enlisted Hawaiians (237.93) was also below the average. The rate for the Philippine Scouts (191.23) was higher than that for the white enlisted men in the Philippine Islands (107.73) and also higher than that for colored troops (122.53) in the same territory.

In general, troops serving in the tropics showed lower admission rates than those in temperate climates. However, the rate for white enlisted men in Panama (210.94) was higher than the corresponding rate in Europe (174.25). The explanation of this is not forthcoming unless it be b ased on the fact that the troops in Europe had passed through the preliminary waves of the epidemic in the United States and had acquired an immunity which was not possessed by the troops in Panama where the earlier waves of the influenza invasion made little imprression. This fact possibly accounts for the relative immunity of the troops in Europe as compared to the corresponding groups int eh Uhnited States. It is not believed that the rates as given for men on transports are comparable fairly with the others, since the difficulty of obtaining a satisfactroy stgrength basis of computation or admission rate is insuperable. The strengths used appear to have been too high and the corresponding rates low. It is generally admitted that during the fall wave of influenza (1918) the incidence and mortality on the transports was high, undoubtedly due to the necessarily limited space available per man.

Among the military personnel during the World War there were 44,270 deaths, occurring in cases having a primary diagnosis of influenza, bronchitis, bronchopneumonia, or lobar pneumonia.¹ Of these, 24,664 are charged to influenza, 439 to bronchitis, 9,022 to bronchopneumonia, and 10,145 to lobar pneumonia. There were, however, large numbers of cases of these diseases reported, secondary to other diseases as previosly stated. If to these associated cases we apply the same case fatality rates as shown by the primary admissions and deaths, we find that there were, in addition to the deaths given above, 189 from influenza, 30 from bronchitis, 1,319 from bronchopneumonia, and 1,184 from lobar pneumonia. This method gives an estimated total of 24, 853 deaths from influenza as recorded, 469 from bronchitis, 10,341 from bronchopneumonia, and 11,329 from lobar pneumonia, a grand total of 46,992. This is nearly as large a total as that of the battle deaths, American Expeditionary Forces--50,385.¹ The disease responsible for the next largest number of deaths was tuberculosis, as a primary admission, with 2,766, followed by measles with 2,370 (also mainly due to pneumonia) and epidemic meningitis, with 1,836.

Of all the deaths charged to influenza, 99.4 per cent were recorded as due secondarily to pneumonia, of which 66.1 per cent of the total were described as bronchopneumonia and 33.3 per cent as lobar pneumonia. It appears that less than 1 per cent of the influenza deaths showed no recognized signs of pneumonia; that a very few cases are fatally overwhelmed by the primary infection appears probable. Of the deaths charged to bronchitis 84.5 per cent were recorded as secondarily due to pneumonia, of which 52 per cent were described as bronchopneumonia and 32.5 per cent as lobar pneumonia, a proportion of 1.6 to 1 as compared with almost exactly 2 to 1 in the cases recorded as secondary to influenza. It is evident atht, in so far as the bronchitis cases were of an influenzal nature, the cases were evidently of a much milder average than those diagnosed frankly as influenza; the greater number of them, too, occurred in the ealrier months of the war period. That this was largely true will be shown later. The men, then who suffered from this infection in a form

severe enough to induce pneumonia and eath were presumably the more susceptible individuals. The proportion of lobar pneumonia to bronchopneumonia is seen to be higher in this group than in those frankly diagnosed as influenza. This agrees with the relations of these types of pneumonia as noted for the white and colored races, in which the more susceptible race showed a much larger relative proportion of lobar pneumonia both in admissions and in deaths.

The total deaths from disease during the war were 58,119, of which those from respiratory diseases (as computed above) were 46,992, or 80.85 per cent. Nearly all of these deaths from respiratory diseases, as has been shown, were the result of pneumonia.

Table 11.--Respiratory diseases. deaths, officers and enlisted men, United States Army, by countries, April 1, 1917-December 31, 1919. Absolute numbers and ratios per 1,000

Table 11.--Respiratory diseases. Deaths, officers and enlisted men, United States Army, by countries, April 1, 1917, to December 31, 1919. Absolute numbers and ratios per 1,000--Continued

	Influenza		Bronchitis		Broncho pneumonia		Lobar pneumonia		Total
	Abso- lute num- bers	Ratios per 1,000	Abso- lute num- bers	Ratios per 1,000	Abso- lute num- bers	Ratios per 1,000	Abso- lute num- bers	Ratios per 1,000	Abso- lute num- bers	Ratios per 1,000
Other countries:
White enlisted men	137	------	3	------	48	------	54	------	242	------
Colored enlisted men	7	------	------	------	13	------	8	------	28	------
Enlisted men, color not stated	2	------	------	------	9	------	5	------	19	------
Total	146	------	3	------	70	------	67	------	286	------
Transports:
White enlisted men	367	3.76	2	.02	80	.83	263	2.70	712	7.31
Colored enlisted men	83	7.88	1	.09	15	1.42	71	6.74	170	16.13
Enlisted men, color not stated	8	------	1	------	4	------	71	------	84	------
Total	458	4.24	4	.04	99	.92	405	3.75	966	8.95
Native enlisted men:
Philippine Scouts	17	.92	------	------	27	1.45	25	1.35	69	3.72
Hawaiians	8	1.42	------	------	------	------	5	.89	13	2.31
Porto Ricans	64	5.41	------	------	3	.89	16	1.35	83	7.65
Total	89	------	------	------	30	------	46	------	165	------

Table 12.--Respiratory diseases. Officers and enlisted men, United States Army, by countries, April 1, 1917, to December 31, 1919. Case fatalities and ratios of bronchopneumonia to lobar pneumonia

Of the race groups, the colored troops show consistently higher rates of death than the whites. The death rates for Porto Rican troops (7.65) is much lower than that of the total colored (19.59) and lower also than the total white rate (9.75). It about equals the rate observed for the white troops in Europe (7.75). In view of their high admission rate, their low fatality emphasizes the influence of the climate in which a large proportion of these men were stationed. This applies also to the low rates for the Philippine Scouts (3.72) and the Hawaiians (2.31). The deat rates for officers (4.87) were lower than for enlisted men (11.09). This difference is more marked in the United States than in Europe. The influence of environment is markedly shown in

Chart VI.--Annual admission rates per 1,000 strength, white enlisted men in the United States, for influenza, bronchitis, bronchopneumonia, and lobar pneumonia, by months, April, 1917, to December, 1919.

the lower death rates for the tropical countries even in groups that show relatively high admission rates as in the case of white troops in Panama (0.56) and in that of the Porto Rican troops (7.65)

Chart VII.--The relations between the annual admission rates per 1,000 strength, white enlisted men in the United States, of the combined influenza and bronchitis and the combined lobar pneumonia and bronchopneumonia, by months, April, 1917, to December 1919.

In attempting to trace the various waves of the influenza epidemic, use has been made of the admission and death rates of influenza, bronchitis, bronchopneumonia, and lobar pneumonia, combined in each case into a single rate. From the pnumber of admissions and the number of deaths, the case fatality has been calculated. Tables 13 to 22, inclusive, and Charts VIII to XIII show these factors for various specific groups of the Army. The epidemic prevalence of influenza in a certain month shows itself on the charts referred to in one or more of three ways, increases beingin the admission rate, in the death rate, or in the case fatality. Differences in race or in length of service are accompanied by differences in the way in which a group reacts to the presence of influenza. When the epidemic is at its worst all three factors are

Chart VIII.--Annual admission and death rates per 1,000 strength for white and colored enlisted men in the United States, total respiratory group of diseases, by moonths, April, 1917, to December, 1919.

markedly affected, but in the case of milder waves only that factor to which the group responds most sensitively may show indications of the presence of the epidemic wave. Thus, in general, the colored race shows less variation in case fatailty and more in morbidity than does the white race. So, too, the process of "seasoning" alters the relation of the case fatailty and the admission rates to the death rates. With these preliminary facts in mind it is possible

to examine the charts of annual rates by months and to determine with some degree of probabililty those months in which an epidemic wave had its occurrence. While statistics classified by weeks would be much more desirable for this purpose, such are not available, and the figures by months give a very clear-cut picture.

Chart IX.--Annual admission and death rates per 1,000 strength for white and colored enlisted men in Europe, total respiratory group of diseases, by months, June, 1917, to December, 1919. (No rates shown when strength was less than 1,000).

Chart X.--Annual admission and death rates per 1,000 strength for white enlisted men in the United States and in Europe, total respiratory group of diseases, by months, April, 1917, to December, 1919.

Chart XI.--Annual admission and death rates per 1,000 strength for colored enlisted men in the United States and in Europe, total respiratory group of diseases, by months, April, 1917, to December, 1919. (No rates shown when strength was less than 1,000).

Chart XII.--Case fatailty rates (per cent), total respiratory group of diseases for white enlisted men in the United States and in Europe, by months, April, 1917, to December, 1919.

Chart XIII.--Case fatailty rates (per cent), total respiratory group of diseases for colored enlisted men in the United States and in Europe, by months, July, 1917, to December, 1919.

Table 13.--Total respiratory diseases (influenza, bronchitis, bronchopneumonia, and lobar pneumonia), white and colored enlisted men, United States Army, in the United States, by months, from April 1, 1917, to December 31, 1919

	Annual admission rates per 1,000 strength		Annual death rates per 1,000 strength		Case fatalitly rates (per cent)
	White	Colored	White	Colored	White	Colored
1917
April	141.97	96.07	2.16	4.92	1.52	5.12
May	113.07	125.53	1.91	------	1.67	------
June	59.53	27.84	.70	------	1.18	------
July	32.74	39.57	.26	1.80	.79	4.55
August	45.60	40.85	.17	1.41	.37	3.45
September	58.23	54.85	.23	2.55	.39	4.65
October	107.58	75.99	.98	2.75	.91	3.62
November	203.84	167.64	3.81	10.40	1.87	6.20
December	312.94	312.28	4.68	22.14	1.50	7.09
1918
January	344.58	308.41	5.83	16.10	1.69	5.22
February	200.08	226.54	2.48	10.81	1.24	4.77
March	363.91	582.10	5.22	10.81	1.24	4.77
April	493.20	649.87	4.63	34.16	.94	5.26
May	167.51	368.70	1.54	16.57	.92	4.49
June	85.94	112.62	.84	4.98	.98	4.42
July	73.13	145.67	.93	5.95	1.27	4.08
August	83.05	197.79	1.27	10.13	1.53	5.12
September	974.36	896.71	54.06	53.86	5.55	6.01
October	1,978.15	1,584.95	95.69	111.66	4.84	7.05
November	296.27	172.86	9.74	6.37	3.29	3.69
December	266.65	191.41	9.08	6.92	3.41	3.62
1919
January	271.90	236.39	9.14	8.09	3.36	3.42
February	138.01	163.75	3.87	4.73	2.80	2.89
March	118.13	134.14	2.30	5.38	1.95	4.01
April	89.37	80.08	1.09	1.61	1.22	2.01
May	65.84	72.73	.79	1.74	1.20	2.39
June	54.24	65.28	.43	1.94	.79	2.97
July	49.99	112.46	.50	1.80	1.00	1.60
August	58.46	29.98	.39	.67	.67	2.23
September	59.46	39.20	.33	1.06	.55	2.70
October	63.40	30.38	.26	1.32	.41	4.35
November	69.42	39.55	.18	1.36	.26	3.44
December	74.78	61.75	.62	------	.83	------

Table 14.--Total respiratory diseases (influenza, bronchitis, bronchopneumonia, and lobar pneumonia) white and colored enlisted men, United States Army in Europe, by months, from June, 1917, to December 31, 1919

	Annual admission rates per 1,000 strength		Annual death rates per 1,000 strength		Case fatalitly rates (per cent)
	White	Colored	White	Colored	White	Colored
1917
June	24.15	------	0.89	------	3.69	------
July	57.04	------	.84	------	1.47	------
August	57.07	------	.24	------	.42	------
September	65.92	------	.17	------	.26	------
October	153.04	------	1.82	------	1.19	------
November	311.49	733.67	1.94	------	.62	------
December	407.17	733.18	2.76	31.39	.68	4.28
1918
January	209.50	969.57	3.60	51.17	1.72	5.28
February	111.70	621.11	1.56	19.87	1.40	3.20
March	125.52	725.57	2.00	33.27	1.59	4.59
April	108.81	662.88	.89	15.15	.82	2.29
May	109.90	421.67	.91	8.06	.83	1.91
June	102.70	265.64	.76	8.67	.74	3.26
July	58.94	189.27	.78	6.10	1.32	3.22
August	73.14	130.62	2.02	7.45	2.76	5.70
September	263.80	473.05	21.05	50.48	7.98	10.67
October	397.00	408.51	33.52	50.75	8.44	12.42
November	200.66	272.07	6.19	11.78	3.08	4.33
December	207.91	266.26	4.42	10.52	2.13	3.95
1919
January	171.32	241.63	5.55	10.77	3.24	4.46
February	223.48	283.59	9.18	12.35	4.11	4.35
March	108.28	160.38	2.23	3.41	2.06	2.13
April	65.84	129.51	.93	2.39	1.41	1.85
May	39.68	68.92	.47	1.09	1.18	1.58
June	30.13	65.64	.71	1.50	2.36	2.29
July	46.32	76.77	.97	1.06	2.09	1.38
August	76.24	82.76	.75	------	.98	------
September	48.69	37.39	------	------	------	------
October	88.89	------	.57	------	.64	------
November	128.73	------	.63	------	.49	------
December	371.41	------	7.19	------	1.94	------

Table 15.--Annual admission rates per 1,000 strength, white enlisted men, in the United States, by months, from April 1, 1917, to December 31, 1919

	Strength	Influenza (all)	Bronchitis	Broncho- pneumonia	Lobar pneumonia
1917
April	183,758	56.03	71.64	2.61	11.69
May	245,454	47.08	55.87	1.66	8.46
June	309,205	21.00	33.26	.85	4.42
July	458,817	10.41	19.25	.39	2.69
August	562,714	14.65	27.77	.66	2.52
September	776,466	20.25	33.72	.94	3.32
October	1,032,244	40.55	55.67	1.62	9.74
November	1,061,422	78.47	100.70	4.44	20.23
December	1,129,065	127.43	157.05	6.23	22.23
1918
January	1,096,434	147.91	161.38	4.51	30.78
February	1,095,039	101.43	78.15	2.18	18.32
March	1,129,223	224.48	117.47	2.91	19.05
April	1,168,558	366.74	106.18	3.31	16.97
May	1,197,757	102.36	56.97	1.79	6.39
June	1,303,746	42.50	37.69	1.27	4.48
July	1,328,513	34.76	33.57	.93	3.87
August	1,284,247	37.32	40.04	1.72	3.97
September	1,321,440	869.54	71.72	14.49	18.61
October	1,343,933	1,823.09	84.77	45.70	24.59
November	1,255,195	203.97	75.26	13.75	3.29
December	941,219	155.26	96.23	10.49	4.67
1919
January	672,937	139.49	116.61	10.95	4.85
February	471,815	56.62	69.97	4.58	3.84
March	406,839	45.57	64.71	4.16	3.69
April	339,836	33.16	49.86	3.28	3.07
May	291,810	16.82	44.38	2.30	2.34
June	246,903	12.73	38.15	1.56	1.80
July	215,104	7.31	38.72	1.28	2.68
August	156,791	8.57	47.14	1.07	1.68
September	149,360	8.68	49.18	.80	.80
October	139,877	10.12	51.82	.60	.86
November	132,403	5.17	62.80	1.00	.45
December	135,441	5.05	67.25	.80	1.68

Table 16.--Annual death rates per 1,000 strength, white enlisted men, in the United States, by months, from April 1, 1917, to December 31, 1919

	Influenza (all)	Bronchitis	Broncho- pneumonia	Lobar pneumonia
1917
April	0.07	------	0.46	1.63
May	.05	------	.20	1.66
June	------	------	.16	.54
July	------	------	.10	.16
August	------	------	.06	.11
September	------	------	.06	.17
October	------	------	.12	.86
November	.01	0.01	.90	2.89
December	.14	.02	1.24	3.28
1918
January	.22	.01	1.04	4.56
February	.07	------	.42	1.99
March	.38	------	.58	4.26
April	.45	.01	.79	3.38
May	.23	------	.33	.98
June	.17	------	.18	.49
July	.37	.01	.14	.41
August	.44	------	.31	.52
September	41.72	.03	5.19	7.12
October	73.26	.02	14.16	8.25
November	6.88	.06	2.05	.75
December	5.58	.08	2.40	1.02
1919
January	4.96	------	3.00	1.18
February	2.14	------	1.02	.71
March	.91	------	.68	.71
April	.42	------	.35	.32
May	.21	------	.29	.29
June	------	------	.24	.19
July	.11	------	.17	.22
August	.08	------	.31	------
September	.08	------	.08	.17
October	.09