Mathers reported that coincident with the epidemic among humans there was an epizootic of so-called influenza among horses. The symptoms are very similar to that of the disease among humans. He isolated a streptococcus as the predominating organism in the horses. The streptococci from human and equine sources, although similar in many characteristics, differed widely in pathogenicity, and seemed to be highly parasitic for the specific hosts.
Capps and Moody found that in man most cases began rather abruptly, with coryza, pharyngitis, laryngitis, or bronchitis.
“The chief complications were inflammation of the accessory sinuses of the head, and bronchopneumonia, the latter being responsible for most of the fatalities. None of these symptoms taken alone would justify the distinctive name of grip. But the widespread and almost simultaneous onset of this fairly uniform symptom group and the rapid cessation of the epidemic after a few weeks reminded physicians generally of the great grip pandemic of 1889–1890. This resemblance was further strengthened by the unusual prostration lasting days or weeks after even mild attacks. The older practitioners can recall no similar epidemic during the twenty-five years intervening between 1890 and this year. The numerous epidemics of septic sore throat have all been entirely different in their symptomatology, and all were restricted to certain localities. The term “grip,” therefore, seems justified from a clinical standpoint.
“The public health reports offer evidence of an unusual prevalence of pneumonia in the larger cities. Nicolas calls attention to the fact that the incidence of grip was greatest in those cities in which the mortality from pneumonia was most strikingly increased.”
Capps and Moody found that as a rule the white blood counts in the individuals sick with influenza were 10,000 or less. A number showed true leucopenia. Less frequently there was a leucocytosis up to 15,000 or higher.
Influenza between 1916 and 1918.—Zinsser cites Dr. George Draper, who believes that he observed at Fort Riley in the winter of 1917 epidemic cases of influenza. He believes that for Europe too there is evidence that influenza was endemic during the years preceding the great outbreak, and that a number of minor epidemic explosions had occurred in the years just preceding 1918:
“MacNeal who has investigated military reports particularly, states that small epidemics occurred in the British Army in 1916 and 1917. A chart constructed by him from the American Expeditionary Force reports shows that a considerable rise in reported influenza cases took place in November and December, 1917, and in January, 1918, gradually declining toward spring. MacNeal, compiling the data available in the office of the Chief Surgeon, A. E. F., states that the influenza morbidity reported per 100,000 for succeeding months in 1917, were as follows:
| July | 321 |
| August | 438 |
| September | 404 |
| October | 1,050 |
| November | 1,980 |
| December | 2,480 |
“Robertson, who studied many of the secondary pneumonias which came to autopsy at this time found an unusual type of lobular pneumonia in which Pfeiffer bacilli were frequently found. In many of these cases the organisms could be obtained from the nasal sinuses and antra. Similar findings were reported by British bacteriologists (Hammond, Rolland and Shore, and Abrahams, Hallows, Eyre and French), who studied the cases that occurred in the reports by Austrian physicians in reference to outbreaks of typical influenza on the Austro-Russian front early in 1917.
“There seems little doubt, therefore, that for some years before the pandemic of 1918 influenza was endemic in many parts both of Europe and of America. As early as 1915–1916 Frost finds evidences of limited epidemic outbreaks in the United States. During the winter immediately preceding the true beginning of the pandemic small outbreaks occurred among the allied troops in France, the British troops in England and probably among American troops gathered in home concentration camps as well. MacNeal in a summary of the conditions prevailing among American troops in France concludes that epidemic influenza in that country originated from the endemic foci there existing, and that the disease was probably carried from Europe to the United States by shipping. The former assumption; namely, that the epidemic occurrence of the disease may have been due to the fact that an enormous and concentrated newly introduced material of susceptibles may have been lighted into flame at the numerous endemic smoulders, may well be correct. The latter, however, concerning the transportation of the disease from Europe to America may justly be questioned. For, in the first place, Frost’s studies have shown that prepandemic outbreaks were quite as frequent in the United States as in Europe during 1915 and 1916, and, though we have no proof of this, there is reason to believe that influenza was prevalent in concentration camps during 1917.”