Part 17

Dotted Line—incidence in the six districts surveyed. ]

The most comprehensive and detailed work that has been done in this line is that reported by Frost and Sydenstricker and by Frost, the first being the result of a canvass of 46,535 persons in Maryland, and the second a similar report based on a canvass of 130,033 persons in several different cities of the United States. We shall have occasion to refer to these later.

MORBIDITY.

There has been great actual variation in the morbidity from influenza in the various epidemics and even in different localities during single epidemics. Previous to 1889 there were no reliable statistics for the disease incidence, and subsequent to that date the records, for the reasons previously mentioned, have still been not entirely adequate.

In the history of influenza morbidity, as in that of its mortality, we must content ourselves for information prior to the nineteenth century with the very general estimates made by contemporary historians. During the last century the statistics have been more numerous and more nearly correct. As far back as the first recognized pandemic, 1510, the extremely high morbidity has been a recognized characteristic. Thomas Short in speaking of this pandemic says, “The disease ... attacked at once and raged all over Europe, not missing a family and scarce a person.”

Pasquier in 1557 spoke of the disease as common to all individuals, and Valleriola describes the widespread distribution of the epidemic throughout the whole of France during that year. It spared neither sex, age, nor rank, neither children nor aged, rich nor poor. The mortality, however, was low, “children only, dying.” Again, Thomas Short remarks, “This disease seized most countries very suddenly when it entered, catching thousands the same moment.”

Of the second pandemic, 1580, Short says, “Though all had it, few died in these countries except such as were let blood of, or had unsound viscera.”

Thomas Sydenham remarks that in the epidemic of 1675 no one escaped, whatever might be his age or temperament, and the disease ran throughout whole families at once.

Molineux recorded concerning 1693, “All conditions of persons were attacked, those residing in the country as well as those in the city; those who lived in the fresh air and those who kept to their rooms; those who were very strong and hardy were taken in the same manner as the weak and spoiled; men, women and children, persons of all ranks and stations in life, the youngest as well as the oldest.”

Schrock tells us that in Augsburg in 1712 not a house was spared by the disease. According to Waldschmidt in Kiel, ten and more persons were frequently taken ill in one house, and Slevogt says that the disease was fearful because so many persons contracted it at the same time. The disease was, however, not dangerous, for Slevogt continues: “Fear soon vanished when it was seen that although it had spread all over the city, it left the sick with equal rapidity.”

It is estimated that in the epidemic of 1729–1730, 60,000 people developed the disease in Rome, 50,000 in Mayence, and 14,000 in Turin. In London “barely one per cent. escaped.” In Lausanne one-half of the population, then estimated at 4,000, was stricken. In Vienna over 60,000 persons were affected. In the monasteries of Paris so many of the inmates were suffering from the disease that no services could be held.

Huxham is quoted in Thomson’s “Annals” as declaring concerning the epidemic of 1732–33: “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.”

Finkler writes as follows concerning the epidemic of 1758: “On Oct. 24th, Whytt continues, the pestilence began to abate. He is not sure whether this was due to a change in the weather, or because the disease had already attacked most people, although the latter seems more plausible to him, particularly as he says that ‘in Edinburgh and its vicinity not one out of six or seven escaped,’ and in other localities it is said to have been even worse. In the north of Scotland also, the epidemic was greatly disseminated from the middle of October to the end of November. A young physician wrote to Robert Whytt: ‘It was the most universal epidemic I ever saw, and I am persuaded that more people were seized with it than escaped.’ This same physician reported that ‘it was not at all mortal here.’”

In the epidemic of 1762, we learn from Razoux, de Brest, Saillant, Ehrmann, that the morbidity was great while the mortality was low.

According to Grimm, nine-tenths of the inhabitants of Eisenach contracted the disease in 1767.

Daniel Rainy, of Dublin, in describing the invasion of an institution in 1775–76, tells us that from among 367 persons varying in age from 12 to 90 years, 200 were taken sick. Thomas Glass says: “There sickened in Exeter Hospital all the inmates, one hundred and seventy-three in number; one hundred and sixty-two had coughs. Two or three days after the hospital was invaded the city workhouse was attacked; of the two hundred paupers housed there only very few escaped the disease.”

Gilibert described an extraordinary morbidity in Russia in 1780–81.

Metzger says that in 1782 the Russian catarrh was so universal during the month of March that in many houses all the inhabitants were attacked. During this period, “in St. Petersburg, 30,000, and in Königsberg, 1,000 persons fell ill each day;” in Rome two-thirds of the inhabitants were attacked; in Munich, three-fourths; and in Vienna the severity of the epidemic compelled the authorities to close the theaters for eight days.

The epidemics of 1788–89, 1799–1800 and of 1802–1803 were characterized by a relatively lower morbidity than that of 1830–32, in which the morbidity was again enormous. Likewise in 1833, the morbidity was very great. In Prague “scarcely a house was spared by the plague.” In Petrograd, 10,000 persons were attacked; in Berlin at least 50,000. These are the figures of Hufeland. The Gazette Médicale records the morbidity as being four-fifths of the total number of inhabitants of Paris.

In 1836, according to Gluge, 40,000 persons suffered from the disease in Berlin alone.

In London, in the 1847 epidemic, it has been calculated that at least 250,000 individuals took sick, and in Paris, according to Marc d’Espine, between one-fourth and one-half of the population developed the disease, and in Geneva not less than one-third.

Leichtenstern informs us that in 1890 the early reports were made by clinical men and were mere presumptions. They were almost universally higher than the later statistical findings. The early estimates for the morbidity in several German cities were from 40–50 per cent. On the other hand, one of the highest statistical reports recorded by Leichtenstern was for Strasbourg in which 36.5 per cent. of the individuals became sick. The average morbidity reported by him ran between 20 and 30 per cent. The difference is accounted for in part by the fact that some of the very mild cases were not recorded in the statistics, and in part by the tendency in giving estimates, to exaggerate.

Auerbach has collected the statistics of 200 families distributed throughout the city of Cologne. He found that 149 of these families (75 per cent.) were attacked. In these, 235 were ill—59 men, 95 women, and 81 children. The larger number of women was explained as due to the illness of the female servants. He estimates each family as consisting on an average of six individuals, and concludes that 20 per cent. were taken with the disease.

Following the 1889 epidemic, Abbott concluded, on a basis of questionaires sent out to various individuals and institutions in the State of Massachusetts, that 39 per cent. of the entire population had been attacked, in all about 850,000 persons.

Moody and Capps, in December, 1915, and January, 1916, made a survey of the personnel and inmates of four institutions in Chicago, the Michael Reese Hospital, the Illinois Training School for Nurses, the Old Men’s Home, and St. Luke’s Hospital Nurses Training School, making a total of 677 persons surveyed, of whom 144 developed influenza, making a percentage morbidity of 21. They remarked that there were many others with colds who remained on duty and were not included in the table and were not diagnosed as influenza.

We have already described the relatively low morbidity and mortality in the early spring epidemic in the United States. According to Soper, the total number affected in March, 1918, at Camp Forrest and the Reserve Officers Training Camp in the Oglethorpe Camps was estimated at 2,900. The total strength at that time was 28,586. The percentage morbidity then was probably a little over 10 per cent. Dunlop, in describing the May, 1918, epidemic in Glasgow, says that it was more limited in extent, as well as milder, than the later epidemic.

It has been estimated that in the autumn epidemic in the United States Army Camps one out of every four men had influenza, and one out of every twenty-four men encamped in this country had pneumonia. During the four autumn months of 1918, 338,343 cases of influenza were reported to the Surgeon General’s Office; there were 61,691 cases of pneumonia.

Woolley reports that among the soldiers at Camp Devens, Mass. 30 per cent. of the population was affected.

At Camp Humphreys, 16 per cent. of the entire personnel developed the disease. The camp had an average strength of 26,600 individuals. Fifty-two per cent. of the entire number of cases occurred during the peak week, which ended October 4th. The outbreak began September 13th and ended October 18th.

Hirsch and McKinney report that an epidemic of unusual virulence swept with great rapidity through several organizations in Camp Grant between September 21, 1918, and October 18, 1918. During this time 9,037 patients were admitted to the Base Hospital, representing about one-fourth of the strength of the camp, and of these, 26 per cent. developed pneumonia. About 11 per cent. of the total admissions or 43 per cent. of the total cases of pneumonia died.

Referring to the report of Howard and Love, we quote as follows: “It is probable that practically all susceptible human material in infected camps suffered from an attack of the disease during the continuance of the epidemic. The records from various camps indicate that from 15 to 40 per cent. of commands suffered from an attack of the disease. These records, as previously stated, do not indicate in full the true incidence of the disease. Certain good results were accomplished in some camps by the application of effective and early isolation of patients and suspects and other measures generally recognized as of value. It was sometimes possible to retard the progress of the epidemic and cause it to be spread over a longer period of time. The epidemic thus became less explosive in character, and fewer people were under treatment at the same time. It was possible to take better care of the sick and thus reduce the incidence of and deaths from complicating pneumonia. It has not been shown that such measures accomplished reduction in the absolute number of cases of influenza occurring in one command as compared with another.

“The ‘cantonment’ group of camps gave a much higher death rate from influenza and its complications than the ‘tent’ camp or ‘departmental’ group. At first glance it would appear that the different housing conditions and the more marked overcrowding in cantonments at the time would fully account for this divergence. Closer study, however, leads to the conclusion that geographical location was a factor of equal or greater importance. It is well known that the disease was most virulent and fatal in the northern, eastern and middle west states, a district in which cantonments predominated. In the southern and Pacific coast states, where the most of the tent camps were located, a milder type of the disease prevailed, with fewer resultant fatalities. Camp Lewis, Washington, and Camp Gordon, Georgia (both cantonments), had relatively low death rates, approximating those in nearby tent camps. On the other hand, Camp Syracuse, New York, and Camp Colt, Pennsylvania (both tent camps), suffered severely and reported death rates approximating those of cantonments in the same geographical district.”

Three waves of influenza are reported by Stanley at San Quentin Prison. During the early wave it was estimated that over 500 of the 1,900 men in the prison population were ill. The wave lasted for a little over two weeks. In the second epidemic there were 69 cases in all, ten per cent. of which developed pneumonia, with two deaths. There were fewer ambulatory cases than in the first. Three and seven-tenths per cent. of the population was attacked in the second epidemic, as compared with 27 per cent. in the first. In the third epidemic there were 59 cases, with no pneumonia and no deaths.

Hernando estimates that in the Philippine Islands, 40 per cent. of the total population of 7,000,000 was stricken with the disease. The epidemic began in June, although it did not become severe until October. The group of ages that suffered most were those between ten and twenty-nine years. Hernando does not believe that the disease was imported because cases were reported before ships arrived from infected countries. After the importation of cases from elsewhere the disease assumed the more severe form.

Armstrong, in reporting a survey of 700 influenza convalescents in Framingham, Mass., remarked that 16 per cent. of the entire population were infected with influenza. Reeks, in a house survey in New Britain, Connecticut, found from among 2,757 persons that the morbidity rate reached 234 per thousand. Dr. Niven found in his block census in Manchester, England, that of 4,721 individuals, 1,108 (25 per cent.) had developed the disease. Fourteen and eight-tenths per cent. of the population were attacked in the summer and 10.4 per cent. during the autumn and winter.

Frost found in his survey of 130,033 individuals that the percentage of the population attacked varied from 15 per cent. in Louisville, Ky., to 53.3 per cent. in San Antonio, Texas, the aggregate for the whole group being about 28 per cent. He remarks that this agrees with scattered observations in the first phase of the 1889–1890 epidemic, when the attack rate seems to have varied within these limits. In five of the localities studied, geographically widely separated, the incidence rate varied only within a narrow limit, from 200 to 250 per thousand. Variations in attack rate showed no apparent consistent relation to geographic location or size of community, or to the rapidity of development of the epidemic.

In a house-to-house survey of 10,000 individuals in Boston the author found that in the winter of 1918–19, 19.71 per cent., or one-fifth of the entire population had developed the disease. It should be pointed out that while the standards used in this survey are entirely comparable to those used by Frost, the author has, contrary to Frost’s method, not included in his group of positive cases those classified as “doubtful.” This would raise the total incidence to a certain extent, but we feel convinced that by omitting the doubtful cases we have approached nearer to a correct picture of the epidemic as it actually occurred. As will be seen from Chart XVI there was no great variation in the different districts studied, with the exception of Districts IV and V. Districts I, II and III were in the tenement section of the city, while District VI was in one of the finest residential parts of Brookline. Districts IV and V were midway between these two extremes as regards economic and sanitary status, as well as extent of crowding. The lowest incidence was in the Irish tenement district. The highest in a middle class Jewish population.

CHART XV.

CHART XVI.

In the 1920 recurrence we found that 9.55 per cent., or one-tenth of the entire population, suffered from the disease, and the arrangement of districts in order of incidence was very little changed. The Irish community suffered least; the two middle class communities most. The well-to-do district in Brookline had the next lowest incidence in 1920. That the high recorded incidence in middle class districts was not due to more accurate or more thorough work on the part of the inspectors is indicated by the fact that a great part of the work on Districts IV and V was done by the same individuals who inspected Districts II and III.

One-fifth of the population studied developed the influenza in 1918–19, and one-tenth of the same population suffered in 1920.

We may agree with Winslow and Rogers, who conclude that the proportion of the population actually affected by the influenza epidemic in 1918 varied between 200 and 400 per thousand.

_Relation of sex to morbidity._—Abbott concluded from his studies in 1890, that the weight of testimony appears to favor the statement that persons of the male sex were attacked in greater number and with greater severity than females. Leichtenstern reached similar conclusions. In the epidemic of 1889, the males were attacked more frequently than the females. He attributes this to two causes: first, the greater exposure to infection, and; second, the fact that strong, robust individuals are more frequently attacked.

It is amusing to compare this explanation with another found in the Medical Supplement to the Review of the Foreign Press for March, 1919. “A Spanish mission composed of Maranon, Pittaluga and Falco visited Paris last October to collect information as to the identity of the Spanish epidemic with the world pandemic of influenza. They found that the epidemics in France and Spain were absolutely identical from the epidemiologic, bacteriologic and clinical standpoint. The great majority of the severe cases in both countries occurred between the ages of 16 and 40. Both in France and Spain more females than males were attacked, which was possibly explained by the greater tendency of the former to lead an indoor existence.”

Jordan, Reed and Fink, working in Chicago, found very different results. They could discover no noteworthy difference among the pupils in high school and elementary school. The attack rate was 230 for the boys and 231 for girls. One sex was presumably as much exposed as the other.

Among the employees of the Chicago Telephone Company, on the other hand, the men were affected in considerably lighter proportion than the women (151 per 1,000 as compared with 233 per 1,000 for women). Jordan believes that the age factor was largely responsible for the difference as the women employees are as a rule of much lower average age than the men.

Frost found that with few exceptions the attack rate at all ages was somewhat higher in females than in males. The total excess of incidence in females was six per cent., which ranged from an excess of nineteen per cent. in the highest locality to a deficiency of two per cent. in the lowest. Only two of the eleven localities surveyed showed a lower incidence among females than among males.

When the sexes were compared in different age groups, the female was found to be higher than the male in each age period except under 5, 10 to 14, 40 to 44, and 70 to 74. The excess of incidence in males in these groups is relatively small, and is hardly significant in the highest age groups, where the rates are computed from small figures. Frost found the most striking excess of incidence in females occurring between the ages of fifteen and forty, the difference between the sexes being relatively slight in age periods above and below these limits. Females over the age of fifteen and especially between the ages of 15 and 45 were either more susceptible to infection, or more generally and more intimately exposed than males of corresponding age.

Our own records by the different age groups were remarkably similar. We have found an excess among the females in every age except under five years, 10 to 14, 50 to 54, and 60 to 64. In 1920 we found a slight excess among the males up to the age of 15, and again at the ages 55 to 65. Females predominated in all other ages (Chart XVII). Among those individuals who had attacks of influenza during both epidemics females again predominated except in the ages under 5 years, 10 to 14 and 55 to 59. In our own results we find that ages above 65 show a predominance of females.

After considering both series of results it is safe to generalize in saying that above the age of 15 the female sex tends to acquire the disease in slightly greater proportion than the male sex.

Chart XV shows the predominance of the female incidence in both epidemics.

CHART XVII.

CHART XVIII.

CHART XIX.

CHART XX.

CHART XXI.

_Relationship of sex to severity._—In classifying cases as to severity, we have followed the standard previously described. Our results have shown that the 1920 recurrence in our group of individuals has been decidedly milder than the earlier 1918 spread. The proportion of mild cases in 1920 is nearly twice that of mild attacks in 1918–19. The proportion of severe cases was twice as great in 1918 as in 1920. The actual severity in 1918 was even greater than would be indicated by these figures. The last column in Chart XVIII is a combination of the two preceding, and while the 1920 column includes all classed as severe, pneumonia, and fatal, that for 1918 only includes the severe and pneumonia cases, but does not include the fatal cases for that year, because those who died during the 1918–19 epidemics are not counted in our 10,000 individuals surveyed. If these were included the percentage of total severe, or average severity would be greater than 42.70.