Influenza

by Warren T. Vaughan

Vaughan and Palmer report for all troops in the United States that, “Without exaggeration it may be said that for the time being at least, influenza and pneumonia suppressed other infectious diseases. Typhoid fever increased to a barely noticeable degree. The death rate from this disease was somewhat higher, but the total number is so small as to barely warrant comment, and not to justify any definite conclusion. Scarlet fever and malaria were both lower than during the summer. In fact, there was but one scarlet fever outbreak of any importance and that occurred at Camp Hancock. Within two weeks over 300 cases were reported and this marks the largest scarlet fever epidemic that occurred in the camps in this country at any time. Meningitis increased although it did not reach the prevalence of the previous winter. The weekly incidence curve for all troops in this country suggests that meningitis was in some instances a sequel to influenza. The greatest meningitis incidence corresponds with the influenza peak. Diphtheria showed no material increase. Deaths from tuberculosis were higher in the autumn than in the two previous periods, the death rate rising from 18 per 100,000 during the summer to 46 in the autumn. The rate for the previous winter was 15.”

In 1889 Abbott was unable to find satisfactory evidence of a connection between influenza and other epidemic diseases, although as he mentions, such connection had often been affirmed. Instances in support of each position were to be found in the literature of the time.

P. Friedrich, after an exhaustive study of the literature, following the 1889 pandemic, concluded that there was no relationship whatever between the incidence of influenza and other acute infections. Wutzdorff reached the same view after studying the various diseases during the influenza recrudescences and recurrences. Finally, Ripperger concluded likewise.

It may be remarked that following 1918 there have been several articles written concerning the relationship between influenza and certain other diseases. These are difficult to correlate and in most instances so many additional factors play a part that the conclusions drawn are perhaps not entirely well grounded. Sylvestri found that in his experience malaria patients escaped the influenza during the pandemic. He believes that it was the malaria rather than the quinine which was responsible for the apparent immunity. On the contrary others have observed, if anything, an increase in malarial patients.

Fränkel and Dublin found that during the pandemic period deaths from whooping cough increased. The difficulty of differentiating between whooping cough and influenza as a cause of death is apparent.

It seems quite certain that deaths from organic diseases of the heart increase during and following influenza epidemics and are due probably to the inability of the weakened patients to resist the added burden. Fränkel and Dublin found an increase in deaths from this cause. This was also observed to be true in Spain and other localities.

Jordan has compared the curves of influenza with those of acute coryza among school children of Chicago and finds that the period of highest incidence of colds in October, 1918, occurred in the second week of school and that it preceded the corresponding period of influenza by seven weeks. There were three peaks in the curve for colds and only two in that for influenza. The period of highest incidence of colds follows the first peak of the influenza curve by one week, while during the week of greatest prevalence of influenza there is a sharp fall of the number of cases of colds. The third peak for colds occurred one week after the height of the influenza curve. As a rule the colds curve runs at a higher level than that for influenza. A striking fact is that the portion of the curve for influenza contained within the period November 23d to December 7th, is almost the exact opposite of the corresponding portion in the curve for colds. How much of this is due to the factor of diagnosis is difficult to say.

Encephalitis lethargica.—It is not within the scope of our report to discuss in detail this disease. Its apparent relationship with influenza, in point of time, if not otherwise, calls for special mention. In 1712 a disease followed a pandemic of influenza, occurring particularly in Germany, where it was known under the name of “Tübingen Sleeping Sickness.” In the spring of 1890, according to Netter, a disease of similar character called “Nona” was distributed especially in Northern Italy and Hungary and scattered more or less diffusely over a large part of Europe. Preceding the last influenza pandemic the disease was first reported in Vienna in the winter of 1916–17. Cases were seen in Paris in February and March, 1918, and the first official report of the disease in England seems to have been on January 26, 1918. In the spring of 1918 there were 168 officially reported cases in England with 37 deaths. The disease seems to have disappeared there in June, 1918, and reappeared in the autumn of the same year. The first cases in the United States were reported by Pothier at Camp Lee, Va. Following the great influenza pandemic cases of lethargic encephalitis have appeared in all parts of the world. It has been present in England, France, Belgium, Switzerland, Austria, Greece, Italy, and other countries of Europe, South America, Mexico, the United States, Australia, Queensland, New South Wales, and Algiers. There was an increase of encephalitis lethargica concomitant with the increase of influenza in the early months of 1920. Thus, in Switzerland 440 cases were reported during February, 1920. The 1920 epidemic of influenza in that country had almost ceased by the middle of March, while that of lethargic encephalitis had greatly decreased. One hundred and forty-one cases of the latter disease appeared in the canton of Zürich alone.

Is epidemic encephalitis a disease sui generis or is it a form of influenza?

The consensus of opinion has been that it is a separate disease. There is, however, no way of telling how close is the relationship to the influenza itself. If lethargic encephalitis is a sequel to influenza, is it caused by the same germ? Flexner points out that in 1916, when the first cases of encephalitis appeared or at least were recognized in Austria, the epidemic of influenza had not yet appeared. In England, France and the United States the epidemics of the two diseases were more or less coincidental. He believes that little weight can be given the supposed coincidence of influenza and the “sleeping sickness” of 1712, and that it is highly improbable that the semi-mysterious affection, “nona,” which dates from 1890 was definitely a sequel of influenza. He concludes that the outbreak of encephalitis either antedated the pandemic of influenza of 1918, or that the two diseases more or less overlapped; that is, although probably quite by accident, they prevailed concurrently. He prefers for the time being at least to regard them as independent diseases.