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Diphtheria—Seasonal variations in age distribution.
In connection with scarlet fever the subject of seasonal variations of age distribution has already
been mentioned (see page 33). The figures supplied by the years 1892-6 appear to indicate that the
maximum proportion of children under five years of age among persons attacked by scarlet fever will
be found in the early part and close of the year, and that this proportion gradually falls until the
months of September or October, when the minimum is reached.
Examination of the figures supplied by diphtheria and which are given below, suggests that the
behaviour of diphtheria in this respect may not be identical with that of scarlet fever, and instead of cases
under five years of age occurring in largest proportion at the beginning and end of the year that this
largest proportion may eventually be found in diphtheria some two or three months later. The month
of August causes an interruption to the fall to September, but as already stated, this fact is evidently
due to the closure of schools in this month. The experience of further years is necessary to determine
more precisely the curve of seasonal age-distribution.