Influenza has been essentially an epidemic disease, appearing in all parts of the world at variable intervals though exhibiting a certain periodicity and seasonal incidence. In addition to epidemic occurrence there have been a number of major pandemics in which the disease has spread with extraordinary rapidity and with a high incidence of morbidity and mortality. The last of these major pandemics was in 1918-1920. Preceding this there was a worldwide occurrence in 1889-1890 and also in 1847. The clinical and pathologic manifestations in all were of sufficient similarity to make certain that in each instance the same disease existed even though the cause was obscure. Epidemics appearing in 1769 and 1737 were probably identical.
Following the pandemic of 1918-1920 the disease recurred, and it has continued to make its appearance in minor epidemic forms in various parts of the world and for limited periods. These subsequent outbreaks, while showing
SLOAN LH, Scupham GW. THERAPY OF THE COOK COUNTY HOSPITAL. JAMA. 1941;116(20):2264–2268. doi:10.1001/jama.1941.62820200008009