The Pandemic of 1918.
The date and site of onset of the great pandemic are subjects concerning which there is no conclusive information. There have been small outbreaks of clinical influenza with epidemic tendencies at one place or another during nearly all of the intervening years since 1889. In all of them the question is open as to whether they were true influenza, and also assuming that some were true influenza, how many of them should be so included. There are some who believe that the increase of morbidity following the measles epidemic in the United States Army camps in the winter of 1917–18 is genetically associated with the great pandemic. In short, there is no one point in the last few years at which we may say that influenza which had previously been non-existent started at a focus and spread throughout the world.
It follows from the experience of 1889 that we should at least attempt to find an endemic focus and to follow the progression of the disease. It is safe to say that once having become pandemic the disease spread as it did thirty years previously. Experience in this country, where the autumn spread began in the New England States and continued West and South; knowledge of the late spread to remote localities; the fact that the disease first appeared in England, etc. in sea coast towns; the introduction of the influenza into new countries at seaport towns, after the arrival of infected ships, all coincide well with the past history.
But which of the several local epidemics of the preceding years was the direct progenitor of the great pandemic? In order to follow more clearly the development of the facts we will record here the various hypotheses that will come up for consideration as to the site of origin of the disease.
1. Influenza is endemic in some one locality, such as Turkestan in Asia, from which place the disease spreads throughout the earth at intervals, after having acquired in some way greatly increased virulence. The local outbreaks of interepidemic times are not due to the virus which causes the great pandemics and should be called pseudo-influenza in contrast to influenza vera. Following the pandemic it is true, however, that for a succession of years local outbreaks occur, due to the pandemic virus which has been left deposited in small endemic foci. These disappear in the course of a few years.
2. The second hypothesis is similar to the first, except that in it is considered the possibility of there being more than one endemic focus, at least two, one in the old world and one in the new. Although Leichtenstern believed in the first hypothesis he did not deny the possibility of the second.
“There have been in the past several well described influenza epidemics limited to North America. Furthermore true pandemics have occurred at the same time in North America and in Europe. We can suggest the hypothesis that there is a permanent endemic focus, just as in central Asia and Russia, existing in the southern part of North America. The following facts concerning the last pandemic period favor this idea.
“As early as May, 1889, influenza began in Athabasca (British North America) and in the summer of 1889, in Greenland. It is especially interesting to hear of an extensive influenza epidemic which in the middle or toward the end of December, 1889, broke out in the Northwest Territory of British North America, in Manitoba, in the Island of Vancouver, similar to that in the east of Canada and Quebec. A spread of the epidemic, which attacked Boston and New York on December 17th, to the above territories, far away and connected by very poor transportation facilities, is certainly improbable, especially in consideration of the time at which the two epidemics occurred.
“We are told that the invasion and the outbreak of influenza in these vast territories occurred at practically the same time at such widely separated places as Fort MacLeod, Saskatchewan, Prince Albert and other military posts, and furthermore in isolated Indian camps and tribes between which there was little or no communication.
“These facts also indicate that we are considering primary endemic pandemics analogous to the one which broke out in July, 1889, in Central Asia.”
3. The virus of influenza is more or less uniformly distributed throughout the world. We may say that it is endemic in many localities, as is the case with the meningococcus. Quite frequently in one locality or another the virus acquires increased virulence and causes a small local epidemic which may even spread to adjoining territories. It is possible that the virus in two or more separated localities may become more invasive simultaneously, thus causing widely separated and unrelated outbreaks. As a rule the virulence does not become so great as to cause a true pandemic, but at rare intervals, usually of decades, or thereabouts, the epidemic virus becomes so greatly enhanced, perhaps from passage to new territory and through non-immune individuals, that it eventually commences on its wild career around the earth. Perhaps the pandemic variety usually comes from one particular locality among the many endemic spots. Perhaps always from the same locality or perhaps at times even simultaneously from many different ones. It is possible even that an increased virulence develops simultaneously in all localities. This third hypothesis develops into a discussion as to whether the small interpandemic epidemics are true influenza or some other disease.
Again, Leichtenstern, although he does not favor it, recognizes the possibility of this theory:
“Whether the small local epidemics reported by Kormann in Coburg in 1878 and by O. Seifert in Würzburg in 1883 are the same as the true epidemic influenza is at present uncertain. Some of the complications, such as swelling of the neck glands, and especially frequently parotitis, purpura, scurvy, indicate that the epidemic in Russia, in 1856–1858, reported by Kasin, was not the true influenza.
“When W. Zülzer writes in 1886 of an epidemic in Berlin in which many thousands of individuals were attacked, the question might arise, is this the same influenza which three years later passed through the entire world and which in Berlin was believed by the same physicians to be a new disease?
“The evidence is better in the case of the epidemic reported by von den Velden in 1874–75. First, because of the complication with pneumonia and especially because at the same time the disease sprang up in several places in France, South Germany and the Rhine Provinces. It is very doubtful whether epidemics described in 1855 and 1862 in Iceland, in 1870 in Philadelphia, in 1875 in Scotland, in 1876 in the Fiji Islands, in 1887 in several places of England, in October, 1889 in Natal, in November, 1889 in Jamaica and Prince Edward Island, was the true influenza, even though the complications of pneumonia in the last named epidemics favor this assumption. As regards the influenza epidemic which attacked specially the school children of Pleshey and Great-Waltham and from which fifty per cent. became ill in November and December, 1889, whereas the pandemic was known to have begun there in January, 1890—the high percentage of school children that were attacked renders the conclusion that this was influenza very doubtful.
“It is an entirely different matter concerning the last epidemic in which the epidemiologic compilations, based on retrospective diagnoses suggest that in many places of Germany the ‘first case’ of even small epidemic outbreaks was observed as early as the summer and autumn of 1889; in other words, several months before the outbreak of the true pandemic in December.”
Leichtenstern believed that the so-called catarrhal fever and epidemics of “cold” which some have been accustomed to call grip or influenza are not the true disease, although he admits that there is no pathognomonic sign by which the diseases may be differentiated. He expected that search for the influenza bacillus which had recently been discovered would enable investigators to determine by its presence or absence whether or not these local epidemics are true influenza.
This, of course, would depend on the proof that the influenza bacillus is the cause of the disease. If the many local influenza outbreaks which Hirsch has collected in his exhaustive historical tables are the same disease as true influenza, then the picture of influenza must be considered as rather protean. Leichtenstern adds that this is a possibility which from present information we cannot deny. He writes: “If such is the case we must give the following epidemiological definition of influenza: Influenza is a specific, infectious disease usually occurring epidemically which, however, is endemic over the entire earth, as indicated by outbreaks of cases, and which, after years and decades have passed, breaks out in epidemic proportions. It is recognized nearly every year in one or another place on the earth where it becomes epidemic. From time to time from some point or center, or from several points, as for instance simultaneously in the old and new world, and for reasons unknown to us, an enormous increase in virulence of the specific virus occurs and with it a great increase in the contagiousness of the disease. Those are the times when influenza spreads in mighty epidemics over wide stretches of land and portions of the earth, or over the whole earth. Our common epidemic influenza or grip, occurring practically isolated or in very small outbreaks, belongs to the same type of disease as the pandemic variety, but is due to a mitigated form of the causative organism, one of decreased virulence and of shorter viability.
“Provisionally, however, we will hold until the proof has been obtained by bacteriological methods that influenza nostras and influenza pandemica are two entirely different diseases, just as are cholera nostras and asiatica. Accordingly, we will divide the diseases designated as influenza in the following way:
“1. Influenza vera, caused by the Pfeiffer bacillus.
“2. The endemic-epidemic influenza vera which arises from the germ remaining after the spread of the influenza pandemic and which is caused by the same germ, the bacillus of Pfeiffer. The duration of this endemic state of influenza vera may last years in single localities.
“3. The endemic influenza nostras, or pseudo-influenza or catarrhal fever, commonly called grip, a disease sui generis. The germs causing this disease are at present as little known as are those of cholera nostras.”
Parkes, in 1876, recognized these possibilities: “The exact spot has not been made out. Two opinions prevail. First, one focus; second, many foci. Each nation, in turn, attributes the disease to its neighbor and from the names so given one can follow the direction of the epidemic.” Noah Webster believed that in 1698, 1757, 1761 and 1781 it originated first in America. Hirsch believed that some of the epidemics had probably originated in North America.
We find then that after the pandemic of the last century the same epidemiologic questions had arisen that have come into such prominence during the present period. As a rule those who have quoted the epidemiologists of 1890 to 1900 have mentioned the first hypothesis and have failed to allude to the fact that the other two were considered. So we see that the subject was by no means settled even at that time, and that if we should discover that the 1918 pandemic cannot be traced to a single endemic focus our results will not be absolutely contradictory to those of the last century.
Returning to a consideration of the period 1916–1918, we observe from reference to Frost’s diagram that in the spring of 1918 there was a sharp and general rise in mortality from influenza and pneumonia. Frost reports that in the larger cities on the Atlantic seaboard this increase occurred generally during January, February and March, when pneumonia mortality normally reaches its maximum. The increase was not so evident in all these cities as it was in New York City. In the rest of the country, especially in the Central and Western States, the increase occurred in April, a month during which pneumonia mortality is generally on the decline, and was sufficient to constitute an unmistakable departure from the normal. The increased mortality rate extended quite generally into May and in some areas still longer. This is the first increase after 1916 that is pictured in the mortality statistics for the country at large.
There are some who believe that they saw influenza in mild form in the United States army in the year 1917. V. C. Vaughan has investigated this possibility and from a study of the sick and wounded charts decided that there was no relation between influenza and the pneumonia which was prevalent in 1917, and which usually was secondary to measles, being caused by the streptococcus in the majority of localities. The lack of association between influenza and pneumonia in 1917 and the direct association in 1918 is well brought out by a comparison of the figures in the two following charts, prepared by V. C. Vaughan:
| Pneumonia as a Sequel to Respiratory Diseases. | |||
|---|---|---|---|
| (All troops in United States in 1917.) | |||
| Primary diseases. | No. of cases. | No. of cases followed by pneumonia. | Per cent. of cases followed by pneumonia. |
| Measles | 47,573 | 2,075 | 4.37 |
| Scarlet Fever | 1,966 | 54 | 2.75 |
| German Measles | 8,982 | 39 | 0.43 |
| Bronchitis | 41,233 | 20 | 0.049 |
| Influenza | 32,248 | 19 | 0.059 |
| Meningitis | 1,027 | 13 | 1.27 |
| Tonsillitis | 43,021 | 7 | 0.016 |
| Pulmonary tuberculosis | 6,799 | 6 | 0.088 |
| Laryngitis | 4,633 | 2 | 0.043 |
| Diphtheria | 1,163 | 1 | 0.086 |
| Mumps | 21,725 | 0 | 0.000 |
| Pharyngitis | 8,096 | 0 | 0.000 |
| Influenza and Pneumonia in Last Four Months of 1918. | |
|---|---|
| Number of cases of influenza | 338,343 |
| Number of cases of influenza followed by pneumonia | 50,700 |
| Number of deaths from influenza-pneumonia | 17,700 |
Stallybrass, who has studied the influenza and pneumonia deaths in Liverpool, England, since the 1889 pandemic, states that in every year there had been reflected in the curves evidence of periodic increase in deaths from influenza and pneumonia, and he states that from 1914 onward there has been a progressive increase in the annual number of influenzal deaths with the single exception of 1917.
It becomes evident that we cannot with the information at hand find any one locality in which the disease was prevalent sufficiently ahead of the pandemic and to the exclusion of other localities, so that we might determine accurately the site of origin. The next step will be, then, to discover as accurately as possible the date at which various communities were first definitely attacked by the great pandemic, and to search out the locality first affected.