“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.” Carnwath, after remarking that the epidemic began in the British Army in France in April, 1918, says that according to the reports of the Influenza Committee of the Advisory Board this was not the first time that Pfeiffer’s bacillus had appeared in the armies. On the contrary, it had frequently been found in cases of bronchopneumonia, especially during the winter of 1916–1917. It is doubtful, however, whether much importance, from the epidemiologic point of view, attaches to these sporadic findings of the Pfeiffer bacillus. Influenza was reported in the year 1917, but this year, as well as the epidemic of 1916, becomes involved in a determination of the date of onset of the great pandemic of 1918. THE PANDEMIC OF 1918.