Influenza

by Warren T. Vaughan

Let us assume that in the interpandemic periods the influenza virus is widely distributed over the earth, existing in an avirulent form. The basis for this assumption is the previously described occurrence of localized epidemics in interpandemic periods. The occurrence of solitary cases, although of interest, could scarcely be considered as evidence of the widespread distribution of the virus, but in the case of the small outbreaks as in 1900, 1907 and 1915, and as in the numerous small outbreaks described by Hirsch, the character of the epidemic curve is characteristic. Let us, then, assume that the disease has been endemic in the United States, together with other localities. It requires no keen observation to discover in the years 1917 and 1918, Theobald Smith’s “movement of individuals and masses from one part of the world to another, whereby the partly adapted parasites become planted, as it were, into new soil, and the original equilibrium is disturbed.” Not only was there a tremendous redistribution and concentration of individuals in our camps in this country, but also there was a further disturbance of the equilibrium in the outbreak of other infectious diseases, particularly measles. The effect of the measles epidemic on the virulence of the streptococcus and allied organisms has been discussed; presumably the same occurred with respect to the influenza virus. Howard and Love report that approximately 40,512 cases of influenza were reported in the United States Army during 1917. They write:

“In 1917, the death rate for the acute respiratory diseases (influenza, pneumonias and the common types) increased to 1.71. During the fall of 1917, after the camps were filled with drafted men, acute epidemic diseases swept through a number of them. Measles was one of the most prevalent and one of the most fatal of the infectious diseases that occurred. It was noted during the fall and early winter that there were a number of cases of pneumonia which were unlike the pneumonia that ordinarily occurred. This was apparent both to the physicians in civil life and in the army camps. It was reported by all classes of practitioners that numerous cases of pneumonia were occurring which resembled the pneumonia following measles, but occurring among men who had not had measles recently. In a number of the camps, both in the north and in the south, rather extensive epidemics of pneumonia occurred and a number of deaths resulted. The same variety of pneumonia occurred in the late winter and spring of 1918. In many of the camps pneumonia was practically epidemic during March and April. In many camps a number of cases occurred later in the spring and summer. It was again reported by a number of medical men that these cases of pneumonia that were occurring were different from the types of pneumonia ordinarily encountered and very similar to pneumonia following measles, but, again, that the cases occurred among men who had not had measles recently.”

MacNeal has observed similar conditions in the American Expeditionary Forces in France in 1917:

“The American troops in France in 1917 began to show, as early as October, 1917, a very considerable rise in the influenza morbidity. The data available in the office of the Chief Surgeon, A. E. F., show an influenza morbidity per 100,000 of 321 in July, 438 in August, and 404 in September, rising to 1,050 in October, 1,980 in November, and 2,480 in December, 1917, in which month the total number of new cases of influenza reported was 3,520. That a considerable proportion of these cases were actual infections with the bacillus of Pfeiffer is proven by the necropsy findings in fatal cases of bronchitis and bronchopneumonia, especially those performed by Major H. E. Robertson at Army Laboratory No. 1, Neufchateau, in November and December, 1917, and January, 1918. In these cases the bacillus of Pfeiffer was found in the scattered patches of lung involved in the bronchopneumonia and also with great frequency in the cranial sinuses. These necropsy findings were, at the time, recognized as essentially new for young adult Americans, and, in a discussion at Army Laboratory No. 1, during December, 1917, they were considered as being of possible important significance for the future morbidity of American soldiers in France. In the British Army in France there is definite evidence of epidemics showing the same pathologic condition, during the winter of 1916–17, and at Aldershot in September, 1917. There can be little, if any doubt that this disease was essentially the same which attacked the American soldiers late in 1917.”

Schittenhelm and Schlecht have reported that a disease was studied among the German troops on the Eastern front which resembled greatly the influenza. It occurred from the beginning of August to the middle of October, 1917. It attacked simultaneously and in epidemic form units and divisions very widely separated over a large territory. It was characterized clinically by a very sudden onset, in the greater number of cases with chill, headache, pain in the extremities, sometimes thoracic pain and cough. The fever lasted seven to nine days. The spleen was enlarged in 11 per cent. of the individuals. There was diarrhea in 12 per cent., frequently conjunctivitis, and quite often a scarlatiniform rash. Bacteriologic examination of the blood was negative. There was usually leucopenia. No treatment seemed especially efficacious. Aspirin gave the best results. The authors call attention to the close similarity to influenza and also suggest that it might have been due to transmission by insects as in pappataci fever or in dengue.

Carnwath concluded that the finding of influenza bacilli in necropsies in British soldiers in 1917 was without epidemiologic significance in considering the origin of the 1918 pandemic. He had studied the disease among the British in detail and appeared to be of the opinion that the first influenza morbidity of significance among the British troops did not appear previous to April, 1918.

MacNeal further says: “The influenza rates per 100,000 of 1,050 in November and 2,480 in December, 1917, really indicate a greater relative prevalence of influenza at that time in the A. E. F. than occurred in the fall of 1918, when the respective morbidity rates were 826 in September, 2,176 in October, and 1,356 in November. The total number of American troops in France was relatively small during that winter—141,995 effective mean strength in December—so that the prevalence of influenza did not lead to the recognition of an actual epidemic. Furthermore, the overcrowding in quarters, which seems to have had a definite relation to many of the later explosive outbreaks, had not become such a distinct feature at that time. In addition, the cold, wet weather, exposure and unusual living conditions furnished explanations for the morbidity which were no longer adequate during the hot weather of May and June, 1918. Until May, 1918, therefore, the prevalence was that of an endemic disease, with perhaps an occasional outbreak suggesting epidemic character.”

We admit that MacNeal’s report furnishes excellent evidence of an independent origin in France. Two points should be borne in mind. First, that MacNeal’s figures are not for the French, but for the Americans who were transported to that country, and that we may consequently consider influenza among the American Expeditionary Forces as being possibly from the same source as influenza among the troops in our own country,—that the American Expeditionary Forces may be considered a subdivision of the American Army in the United States, equally well as a subdivision of the French population; second, that we have been unable to find detailed evidence of similar conditions occurring among the French troops or French population, where the conditions have been ripe in a way since 1914. MacNeal records that in March and April, 1918, there was a great increase in the number of troops brought over from the United States to France. Previous to that time there had been 287,000 in that country and during the two months 150,000 were added, with a consequent increase of more than fifty per cent.

We should insert a word of caution regarding the diagnosis of influenza among troops in the absence of any sign of an epidemic. Internists who served in base hospitals during the war will agree that a diagnosis of influenza is very frequently made on the admission card when the disease turns out to be some other malady. This was not equally true in all camps, but regimental surgeons could often be found who would transfer a patient to the hospital with the diagnosis of influenza used almost interchangeably with the diagnosis “Fever of unknown origin.” It would be interesting to see statistics from one or two of those base hospitals which were manned with especially competent internists, as to the frequency with which the admission diagnosis of influenza remained unchallenged in the hospital, during the year 1917.

There would be such cases in greater or smaller numbers. The magnitude of this number would not influence our hypothesis.