Influenza

by Warren T. Vaughan

Asiatic cholera.—There are those who claim that the disease should be compared with Asiatic cholera which remains constantly endemic on the banks of the Ganges and at intervals spreads from there throughout Indo-China, and formerly at times throughout the civilized world. Those who compare influenza with this disease believe that this is additional evidence in favor of a single focus of endemicity of influenza.

Epidemic meningitis.—On the contrary the disease may well be compared with epidemic meningitis. The germ of this disease, distributed throughout the world, is usually in an avirulent form and produces no epidemic of meningitis. Only an occasional case arises. There are certain localities in which the disease is particularly prevalent at all times. We may speak of these as endemic foci, but must remember that at the same time the virus is distributed elsewhere. Thus South Carolina, Missouri and Kansas have been shown to be localities in which meningitis has been more or less widely distributed for some years.

We can carry the analogy still farther. During the concentration of forces early in the war, camps were established at Columbia, S. C. and at Fort Riley, Kansas. In these camps, Jackson and Funston, there very rapidly developed quite extensive epidemics of cerebrospinal meningitis. Here and in Camp Beauregard, the incidence of the disease was out of all proportion to that in the other camps. Just as the exaltation of virulence of the influenza virus has been favored by gross changes in the environment, the occupation, the density of, and the disease incidence in the host as a community, so also do these appear to have been factors in the development of a meningitis prevalence in the army. It was more prevalent in those camps situated in the territories where the disease was particularly endemic, but was also present in all camps. Had the meningococcus been able to assume the high degree of virulence and invasiveness possessed by the influenza virus it is reasonable to assume that a pandemic spread would have begun in one of the two or three camps where the disease was especially prevalent. It would have spread thence and have attacked those camps in which a mildly virulent meningococcus had already been causing disease. Just as in influenza the pandemic spread would have been due not to the universally distributed virus, but to the one or few which finally acquired the greatest exaltation of virulence.

We see then that the followers of both theories—that of the single focus and that of an extensive distribution—can quote other infectious diseases in support of their theory, but the evidence in favor of similarity to Asiatic cholera is not complete. The disease is not similar. The mode of transmission is entirely different. The infection is chiefly of the gastro-intestinal tract, while that in influenza is chiefly respiratory. Since 1816 there have been five pandemics of Asiatic cholera, the last occurring in 1883 and all of them traceable to a primary focus in India. Frequently it was carried from India by the faithful, to Mecca and from there was readily distributed throughout Europe. In the last pandemic the disease spread throughout the old world and reached New York harbor, but was refused admission.

Plague.—The similarity in clinical symptomatology, in gross pathology and the apparent similarity in manner of spread and epidemic features between influenza and the pneumonic form of plague has suggested to some that the best comparison should be made with the latter disease. Here again is a disease which is endemic in Asia and spreads elsewhere only at intervals. If we go back into the history of the plague we will discover that formerly it was distributed more or less throughout the civilized world. The plague is supposed to have been known to the children of Israel at the time of the exodus from Egypt. The Egypt of the Pharaohs was a country of great salubrity. Hygienic measures were excellent. The inhabitants built aqueducts, disposed of their dead hygienically, reared temples, maintained law and order, developed the elements of literature and science and devised and employed simple machinery. But as early as the exodus, Egypt had lost its salubrity. This is indicated by many passages in the Bible. The plague was present in that country during this period. Sticker believes that the pest among the Philistines spoken of in the First Book of Samuel, when the captured army was returned with five golden emerods and five golden mice, was the bubonic plague.

Thucydides describes a plague in Athens occurring before Christ. This is generally believed to have been “the plague.” The time of the earliest appearance of the disease in Italy is not known but it was well established there in the first century of our era. The plague was endemic in Italy at that time and it developed in epidemic form with each increase in susceptible material. At about 68 A.D. the disease spread over the whole of Asia, Northern Africa and Europe. Exacerbations of the disease are described in the years 80, 88 and 92 A.D. In Rome they occurred in 102, 107 and 117 A.D. The disease was present in Wales in 114 A.D. In 167 an unusually severe outbreak of the plague occurred in Rome. There were other outbreaks in the Roman army in 173, 175 and 178. Had we the space to record here the history of the plague we would find that the disease was widely distributed throughout Europe for several hundreds of years, that it was particularly prevalent in certain areas and that at intervals it spread from one or a few foci, throughout the continent.

We can compare the epidemic features of influenza with these other contagious diseases, but we will always find some points of difference from one or another. Let us consider again for a moment epidemic meningitis. There is no combination of predisposing causes, environmental, meteorologic or bacteriologic which will produce epidemics of cerebrospinal meningitis in the absence of the meningococcus itself. The organism causing the disease must be present before the disease will occur. The specificity of the invading organism in the different diseases will always produce some variation among the epidemiologic features. Other things being equal, that locality in which this germ is most extensively distributed will be the locality in which epidemics, when they do break out, will be most extensive.

In the case of our army camps, those individuals carrying the disease virus from the endemic foci to the camps were not the ones who fell ill. Generally it was those, coming from other areas in which meningitis was not extensively distributed and who had, therefore, not acquired an increased resistance to the disease, who fell ill. But after the disease had acquired increased virulence at Camp Jackson, not only did it occur in the troops at that camp, but it also became quite extensive throughout the civilian population, presumably among those who had previously been exposed to it in its endemic form.

In our comparison of influenza with other infectious diseases we wish to show particularly that the disease is not in a class by itself, but that its epidemiologic features are not unlike those of other respiratory infections, that the manner of spread and the mode of infection are similar to those of the other diseases. Nothing unusual or unknown need be called into use in explaining any differences. Those differences that very palpably exist can be explained by facts which we already know. Leichtenstern, thirty years ago, believed that the disease was similar in its manner of spread to other infectious diseases. He observed this particularly in the earliest and the latest phases of epidemic spreads where cases were scattered. He saw that in households the disease attacked some and spared others even of those intimately connected with the sick, just as was the case in diphtheria or meningitis. He writes: “Comparing these later periods the disease evidences the same contagious characteristics as the other endemic contagious diseases, such as scarlet fever, measles, diphtheria, epidemic cerebrospinal meningitis, etc.”

Parkes made very similar observations even before the 1889 epidemic.