Part 21
Let us consider in greater detail the fate of both rural and urban individuals who had been recently drafted into the military forces of this country. Almost universally the raw recruit was found more susceptible to disease than was the seasoned soldier. A report by Lieutenant W. D. Wallis from Camp Lee “shows that while those who had been in the service less than one month constituted only 9.19 per cent. of the total strength, they furnished 30.11 per cent. of the total deaths from influenza and consequent pneumonia. Furthermore, it is shown that while those who had been in the service from one to three months constituted 45.18 per cent. of the camp, they furnished 46.24 per cent. of deaths. On the other hand, those who had been in the service more than three months constituted 46.63 per cent. of the population and furnished only 23.69 per cent. of deaths.
Lieutenant Wallis says: “These figures show a much greater percentage of deaths for the first month in camp than the corresponding proportion of the population would warrant; while in the period of three months or more of service the percentage is less than half of that of the camp population having this length of service. The only approach to a correspondence is in the period from one to three months where the respective percentages differ but little. The increase in length of service is accompanied by a progressive decrease in the percentage of deaths from 30.11 per cent. to 27.41 per cent. to 18.87 per cent., although only 9.19 per cent. of the population in the camp falls within the class of less than one month’s service.
“The incidence of mortality is in the first month’s service more than three-fold the percentage of the number of men; and in the period of three months or more of service is scarcely more than half of the percentage of the number of men of the camp in that group.
“The fact that the case mortality is higher among those who came from rural homes than among those who came from cities seems to hold even after three month’s of service, or more.”
Vaughan and Palmer found that the case fatality at Camp Dix among those who came from cities with a population of 10,000 or more was 10.8; while among those who came from more rural homes the rate was 15.8, although the average service of both groups was the same.
The Camp Surgeon of Camp Grant concluded from his records that the new recruit is more susceptible to influenza and is more apt to succumb than is the man who has been trained and is accustomed to Army life.
Wooley reports data collected from four Infantry organizations at Camp Devens comprising 15,502 men. Of 9,559 men who had been in camp less than five months, 3,575 or 37.5 per cent. developed influenza, whereas of 5,943 men who had seen more than five months service in the army, 1,033 or 17.5 per cent. developed the disease. He concludes that the large number of recruits in the camp certainly was a factor in increasing the disease incidence. It should be remarked that Camp Devens appears not to have had any influenza epidemic in the spring of 1918.
It is to be regretted that we have not several reports dealing with the same subject from camps where the disease was definitely recognized in the spring. Fortunately we have one such. Opie and his co-workers have observed that the epidemic at Camp Funston, which occurred between March 4th and March 29th, 1918, and which attacked 1,127 out of a total of 29,000 men, involved chiefly the organizations which had been at Camp Funston during six months or more. At that time it seems to have infected all susceptible individuals, and to have spent itself. Subsequent waves of influenza, four in number, and coming at a little less than one month intervals, occurred when newly drafted men were brought into the camp in April and May. In these latter cases the disease affected the men newly arrived in camp.
At Camp Funston, at least, the higher incidence in the raw recruit appears to be explained in part by a relative immunity of those who had been in camp a month or more, existing as a result of an earlier prevalence of the disease. More abundant evidence would, however, be necessary before we could deny a diminution of natural immunity in the recruits, caused by the exposure, overwork, fatigue, and change of daily routine. As V. C. Vaughan has remarked: “It appears that natural immunity gives way before exposure, overwork and fatigue, as was demonstrated years ago by Pasteur in his experiments on birds with anthrax. Likewise, it is possible for human beings to have their resistance lowered by exposure to unaccustomed environment, so that although naturally immune, the standard of immunity is reduced to the point where the influenza virus gains admittance and overcomes the lowered resistance.”
_Race stock and mortality._—The relationship of morbidity to race stock has already been considered and should be borne in mind in a discussion of mortality by race.
We have seen how the natives of India suffered unusually from the influenza, the total deaths being estimated at over 5,000,000 individuals. A preliminary report from the Department of the Interior on the mortality from influenza among American Indians showed that during the six months period from October 1, 1918, to March 31, 1919, over two per cent. of the Indian population died of influenza. The mortality among Indians in the Mountain States, especially in Colorado, Utah and New Mexico, was very high. For the Indian population as a whole the annual mortality rate from influenza alone during the six months period was according to the U. S. Public Health Reports 41.2 per 1,000, which is above that for the larger cities in the United States during the same epidemic period.
In both of the above races we cannot say that it was not factors other than race, particularly living conditions, that resulted in the high mortality.
Winslow and Rogers found in Connecticut that the proportion of influenza-pneumonia deaths was lower than would be expected among persons of native Irish, English and German stock, but higher than would be expected among Russian, Austrian, Canadian and Polish stock, and enormously high among Italians. They suggest that this marked difference in racial incidence may be very largely due to the differences in age distribution of the various race stocks, the races showing the highest ratios being those which have arrived more recently in the country and which are made up more largely of young adults at the ages which suffer most severely from influenza. They further refer to the work done by Armstrong in Framingham, and state that their results tend to confirm his conclusions in regard to the Italians, as do the figures presented by Greenberg from the records of the Visiting Nurse Association of New Haven. “It appears that Italy suffered very severely from the influenza epidemic in Europe, and Dublin has shown that the normal pneumonia rate of this race is a very high one.”
We have rather more abundant comparison of the white and black races in this country. Frost found in his extensive survey that the case fatality was generally higher among the colored than among the white population. A similar observation was made by Howard and Love, who found that the case mortality for influenza and its complications in the United States and in the American Expeditionary Forces, in 1918, was for colored troops 4.3 per cent. and for white troops 3.3.
These two series of observations are of great importance, for they are about all we have describing case fatality rate. The majority of other reports describe mortality rate only, and are therefore not complete.
The death rate in the Army was higher among colored troops, but the incidence of influenza, the rate per 1,000, was lower for the colored race. “Considering only the southern states, the nativity rate for influenza for the white was 247.11 and for the colored, 154.58. For lobar pneumonia it was 10.77 for the white and 28.31 for the colored; for bronchopneumonia and unclassified pneumonia 7.26 for the whites and 11.43 for the colored. It seems probable that the negro is less susceptible to influenza than the southern whites, but that he is much more susceptible to pneumonic infections, either primary or secondary.”
Fränkel and Dublin have studied the racial distribution of 70,729 deaths among policy holders of the Industrial Department of the Metropolitan Life Insurance Company, particularly with respect to incidence among white and black. Normally the mortality from respiratory diseases is higher among colored persons than among whites. In the seven year period from 1911 to 1917, influenza-pneumonia death rates showed an excess of 72 per cent. colored males over white males and of 56 per cent. colored females over white females. During the period of the epidemic the situation was reversed. The whites suffered from higher rates than the colored. While the rate among white males during the period, October to December, 1918, was nearly fifteen times as great as during the period 1911 to 1917; that of colored males was only seven times as great as the rate during the same seven year period. White females during the height of the epidemic showed a rate more than sixteen times as high as the normal, while colored females experienced a rate only nine times as high. After the first of January, 1919, the excess rate returned slowly to the normal figures. These facts are based on death rate only.
Any comparison of race morbidity or mortality, to be of value, must be based on observations of individuals living in the same climate, in the same domestic environment, and in similar age distribution. It is practically impossible to discover groups living under such conditions. Howard and Love, perhaps, approached more nearly to such an ideal in studying the white and black races in the Army, but even in the military forces many factors are at play. Thus, the death rate among enlisted men was highest among the American troops in the United States (12.02); second in Europe (6.07); third in Panama (1.09); fourth in Hawaii (0.55); fifth in the Philippine Islands (0.14). By race it was highest for the colored troops (12.69); second for the white (8.83); third for the Porto Ricans (7.80); fourth for the Filippinos (2.84); and fifth for the Hawaiians (1.72). The authors point out that while the native troops had higher admission rates than the whites, the death rates were lower, which illustrates the point that the death rate for this type of disease is lower in the summer and in the tropics.
SECTION IV.
AN INTENSIVE STUDY OF THE SPREAD OF INFLUENZA IN SMALL GROUPS OF CLOSELY ASSOCIATED INDIVIDUALS.
We have been discussing the disease under consideration chiefly from the viewpoint of the statistician. The statistician, possessing a wealth of information of a general nature, and from all parts of the world, and armed with fascinating complex mathematical instruments, is able to dissect the information at his disposal, and to reconstruct therefrom both facts and apparent facts of absorbing interest. To him we are indebted for the bulk of our knowledge of the distribution and spread of the influenza through metropolises, through countries, and through continents.
Like the aviator flying over enemy territory he acquires a breadth of vision and a general perspective which is to a great extent denied to those remaining on the ground. But also like the aviator, from the very fact of his high position he loses the ability to recognize detail. The small subdivisions in the enemy lines are slightly blurred and he can distinguish the front line trenches in which most of the action is occurring no more clearly than the reserve and support trenches. An Army depending entirely upon its aeroplane reconaissance would find itself helpless in combating the enemy. The aeroplane is useful, yes, it could not be dispensed with, but never an opportunity is lost for scouting parties to explore the enemy front lines; it is these latter who bring back information as to the local strength and distribution of the enemy, as to what particular divisions are in action, as to the strength of the entrenchments, the enemy distribution within the trenches, and finally what is most important, information as to the weak points in the enemy’s lines, places at which we may concentrate our attack with the hope of driving the enemy from its stronghold. Occasionally a raiding party will return with a prisoner. He will be examined thoroughly and may yield some valuable information. All such prisoners are not dressed alike. We recognize that some belong to one regiment and some to another. After we have extracted what information we can from the prisoner he is incarcerated, if we may extend our metaphor, in a test tube, and there he remains for future reference. We do not believe that these individual private soldiers are the cause of the war, but we do know that they are doing their share of the killing—that they are doing most of the killing.
It is characteristic of human enthusiasm and hopefulness that each raiding party prays that it may bring back with it a general officer, a field marshall, the one who is chiefly responsible for the enemy offensive. In our own little battle with our invisible host we have long since discovered that field marshalls here as elsewhere are difficult to discover by raiding parties. But the raids are and should be made just the same. They almost invariably bring back some new item of information, and it is the experience of many wars that even though the commanding general be never captured, repeated small or large attacks following preliminary reconaissance, if diligently and valiantly prosecuted under good leadership may win the war.
In studying the life and habits of the influenza virus and its army of secondary invaders, and the results thereof in small groups composed of individuals as the unit, instead of large groups with communities as a unit, we will be able to discover a certain number of additional facts, some of which may have considerable value.
In the study by the author of six selected districts in Boston a special study was made of the occurrence and manner of spread of the influenza in the household or family as a unit. The 10,000 individuals canvassed were distributed through 2,117 families. Of these two thousand odd families, 45.44 per cent. were visited with one or more cases of the disease in the 1918–19 epidemic, and 27.25 per cent. in the winter of 1920. Of these, 14.31 per cent. had cases in both epidemics. In either one or both of the two epidemics under consideration, 58.38 per cent. of all families had influenza (see Table III).
TABLE III. _Per cent. of families invaded by influenza._ ═══════════════╤═════════════╤═════════════╤═════════════╤═════════════ Boston District│ 1918–19. │ 1920. │ 1918–19 and │ Total. No. │ │ │ 1920. │ ───────────────┼─────────────┼─────────────┼─────────────┼───────────── 1 │ 49.59│ 32.79│ 20.05│ 62.33 2 │ 36.04│ 17.36│ 7.25│ 46.15 3 │ 45.89│ 26.43│ 14.71│ 57.61 4 │ 48.48│ 32.20│ 14.39│ 66.29 5 │ 52.48│ 34.11│ 19.53│ 67.06 6 │ 43.16│ 24.21│ 11.23│ 56.14 All Districts │ 45.44│ 27.25│ 14.31│ 58.38 ───────────────┴─────────────┴─────────────┴─────────────┴─────────────
Explanatory note: 45.44 per cent. of all families were invaded in 1918.
27.25 per cent. of all families were invaded in 1920.
14.31 per cent. of all families were invaded in both epidemics.
58.38 per cent. of all families were invaded in one or the other or both.
41.62 per cent. of all families remained free from influenza throughout both epidemics.
In this discussion of family incidence, as in our work on the incidence among individuals, the question naturally arises as to the reliability of our information and the accuracy of our results. We have shown the close correspondence between our own results and those of Frost, done on a vastly larger number of individuals. The information for families was obtained from the same sources and from the same individuals. The thoroughness with which the inspectors did their work is indicated by the fact that in addition to the 2,117 families on which we base our results, only the records of 194 families have been discarded for various reasons. In discarding the family records we also discarded the individual records and such are, therefore, for individuals above our total of 10,000. One hundred and fifty-four of these were for families whose homes were in the districts surveyed, but who were not at home at the time of the first survey. These were omitted during the second survey, irrespective of whether individuals were at home. In this group are also included a few in which children were at home, but were unable to give reliable information. Fifteen of the 194 families gave insufficient information, and 25 refused to co-operate. The small number in this last group speaks well for the efficiency and methods of the inspectors. All families accepted for tabulation co-operated to the best of their ability, and we believe that the records are as accurate as this type of work may be made.
Dr. Niven, in the work referred to by Carnwath, made an inquiry covering 1,021 houses, with a population of 4,721. Five hundred and three households or almost exactly one-half, were invaded in either the summer 1918, or the autumn-winter 1918 epidemic. This proportion of families is quite similar to our own, but it must be pointed out that Niven was not studying the same two epidemics that we are discussing. Two hundred and sixty-six of his total households, or 26.05 per cent. were invaded in the autumn epidemic.
Previous to the present time the author has been unable to find records of investigators having used this method of studying influenza to any appreciable extent. Certainly there has been nothing done on the subject previous to the last pandemic. Since then Frost has studied, as indicated in his report, family incidence to the extent of determining the relationship to overcrowding and to economic status, and Niven has studied family incidence with special reference to immunity.
Thomas Sydenham, speaking of the epidemic of 1675, says that: “No one escaped them whatever might be his age or temperament, and they ran through whole families at once.”
According to Waldschmidt, during the epidemic of 1712, in Kiel, ten or more persons were frequently taken ill in one house.
In 1732, Huxam tells us that, “not a house was free from it, the beggar’s hut and the nobleman’s palace were alike subject to its attack, scarce a person escaping either in town or country, old and young, strong and infirm, shared the same fate.”
Metzger says that the influenza was so universal in March, 1782, that in very many houses all of the inmates were attacked. On the other hand, Mertens did not believe the influenza a contagion during the same epidemic for the reason that according to his observations now only one, and again all, of the members of a family, were stricken.
In 1833, in Königsberg, according to Hufeland, parents, children, and servants were frequently smitten with the disease at the same time, so that strange help had to be obtained for the family.
Parkes taught that, “Persons in overcrowded habitations have, particularly in some epidemics, especially suffered, and several instances are on record of a large school or a barrack for soldiers being first attacked, and of the disease prevailing there for some days before it began to prevail in the town around. Sometimes, on the other hand, schools and prisons have escaped. A low, damp, ill-ventilated and unhealthy situation appears to predispose to it, and in some instances, in hospital patients, it has assumed a malignant character. In other cases again, hospital patients have escaped; for example, the old people in the Salpêtrière in 1837, when the younger attendants were attacked.”
_Effect of overcrowding._—The family or household forms a social unit in which human intercourse is very close, and in which the opportunities for contact infection either direct or indirect are manifold. In addition to all of the opportunities which each individual has for contracting the disease outside of the family every case in the family exposes every other member many times during the day. One of the first questions arising in a study of the disease in the family is, therefore, whether the size of the family in and of itself exerts any predisposing influence on the total incidence in any one family. Are large families more likely to have a greater percentage of cases than small families? We have endeavored to answer this question by grouping together all families containing only one individual, all of those with two, three, four, etc., and determining the percentage of individuals contracting influenza in each of the groups. The standard for comparison is the percentage of the total 10,000 who contracted the disease in either year, or in both. 19.71 per cent. of all persons canvassed contracted influenza in 1918–19. Reference to Table IV shows that of persons living in families of one, 17.95 per cent. developed the disease; of those in families of two, 18.46 per cent.; in families of three, 19.96 per cent.; in families of four, 20.10 per cent.; and in families of from five to seven, between 22 and 23 per cent. Families of over seven all showed lower, but varying incidence of the disease. As is seen by the table, they comprise only a small number of families.