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October 7, 1939


JAMA. 1939;113(15):1416-1417. doi:10.1001/jama.1939.02800400044012

Like other epidemic diseases, influenza tends to fluctuate in its frequency and in its virulence. Furthermore, this intermittence was evident not only in the case of the great pandemics, such as the one of 1917-1918, but also in the minor epidemics which occurred both before and after that calamity. It has been difficult however to relate the fluctuations which actually occurred with any definite time or seasonal factor. When the literature on influenza was reviewed by Jordan1 in 1927 the theory of Brownlee, who attempted to relate endemic "influenza" to a periodicity of thirty-three weeks, was dominant. Jordan pointed out, however, that the evidence available was not sufficient to establish definitely the conclusion that a nonseasonal cycle as predicted by Brownlee was an inherent and general characteristic of influenza in postpandemic periods, because the observations did not cover a sufficient number of different areas to give them generality, because