"The site of origin of the great pandemic of 1918 is unknown, but some choose to think that it was in the United States. Scattered outbreaks of disease were detected during the spring and early summer of 1918. Excess pneumonia-influenza deaths were evident from later tabulations by Wade Hampton Frost, who directed most of the epidemiologic investigations of this pandemic for the US Public Health Service. Many of the early outbreaks occurred in military installations as recruits poured into training camps to respond to the call for troops in Europe. Outbreaks also occurred on troop ships and among the American Expeditionary Forces in France by April 1918. The disease was soon evident among allied forces. A period of quiescence was noted in the United States during the summer. In some areas it was suspected that a reintroduction from Europe occurred in late summer and early autumn. However, in retrospect, it is evident that “seeding” of many geographic areas of the United States had occurred during the previous spring, that transmission was low during the summer but picked up rapidly as schools reopened in September. The first wave of the pandemic reached a crescendo by the end of October 1918. This was followed by a decline and recrudescence in midwinter 1919. The same pattern of occurrence was observed in the United States in 1957 with the next pandemic caused by influenza A (H2N2) (20)."