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It will be seen from the table relating to 1894 (page 24) that the scarlet fever case mortality
reached its maximum in April and its minimum in October, the case mortality in the former month
being nearly twice as great as that in the latter.
In order to ascertain whether the difference in the case mortality of the disease in these two
months was due to differences in the age and sex distribution of the cases, I have prepared the following
table, showing for each sex at several age periods what would have been the deaths had the case
mortality been in April and in October the same for each age and sex as actually occurred over the
whole vear 1894.
It thus appears that had the case mortality at each age and for each sex been the same in each
of these months as in the whole of 1894 the number of deaths occurring among the 1,631 cases of both
sexes notified in April would have been 85*52, giving a case mortality at " all ages" of 5 24 per cent.;
similarly among the 1,809 cases of both sexes notified in October, the deaths would have been 96.73,
and the case mortality 5.35 per cent. It is therefore apparent that the difference between the actual
case mortalities in the two months in question, viz., a difference between 6'87 and 3.65 (the case
mortalities shown in the table for 1894) is not explicable on the ground of a difference in the age and
sex distribution of the cases notified.
It is obvious, therefore, that as the case mortality varies at different periods of the year, the
"seasonal " distribution of the cases notified must influence the case mortality at " all ages " calculated
on the figures for the whole year. Thus in 1893 a much larger proportion of the cases in that year
occurred in the late summer and autumn months than in 1894, a circumstance that would tend to
make the case mortality of 1893 lower than that of 1894. In point of fact, it may be stated that if
correction be made for all the causes of variation pointed out, the " all ages" case mortalities of 1893
and 1894 become practically identical. The subject evidently needs farther investigation, but the
inquiry already made points to the following conclusions—
(a) That after due correction for differences in the age and sex distribution of the cases
notified, the case mortality of scarlet fever varies to a considerable extent at different periods
of the year.
(b) That in comparing the case mortality at " all ages" of one year with another due
correction must be made for—
(1) Differences in the age and sex distribution of the cases notified, and
(2) Differences in the " seasonal" distribution of the disease.
Hospital accommodation.
It will be seen by reference to diagram VIII. that the percentage of cases notified in London admitted
to the hospitals of the Board was higher than that of any preceding year, the number of cases admitted
during the year being 11,598 or 62.9 per cent. of the total cases notified, and the number of deaths
occurring in these hospitals being 717 or 74.6 per cent. of the total deaths registered in London from
this disease.
Scarlet fever and elementary schools.
In my last report I discussed the subject of the part played by elementary schools in the
dissemination of scarlet fever, and showed that a marked decrease in the number of cases notified
occurred in 1892 and 1893 at a time which corresponded with the summer holiday of the children
attending London School Board schools, and that there was a marked increase in the number of cases
notified at a time which corresponded with the re-opening of these schools at the close of the holidays,
due allowance being made for a period of incubation and for a little delay in notification. Also I showed
that this decrease was especially marked in the case of children at the school age period of life.
With a view to learning whether the experience of the year 1894 points in the same direction
as that of the two preceding years, the notified cases in each week of the year have been divided into
three age groups, viz., children under three years of age, children from 3 to 13, and persons above
13 years of age.
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