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September 4, 1943


Author Affiliations

President, Chicago Department of Health.

Epidemiologist, Chicago Department of Health.

JAMA. 1943;123(1):53. doi:10.1001/jama.1943.02840360055022

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To the Editor:—  Plotting the weekly trend of poliomyelitis in Chicago for the two highest years on record—1917 and 1937 —revealed an interesting phenomenon common to the two years. Histograms of the cases reported each week in these two years as well as that of 1943 are shown in chart 1; the cases are not shown, as they were negligible. The trend starts up slowly for the first few weeks, then rapidly gathers momentum as the slope changes from a horizontal to a vertical position; on the way down from the peak the picture is almost duplicated.Since case reports are likely to come in irregularly, a curve smoothed by three week moving averages was used in chart 2. The symmetry of the 1917 and 1937 curves ent. The resemblance to a normal curve, even to the asymptotic tails on both ends, is remarkable. Also included in the chart are

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