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42
At this stage it may be advisable to consider the corresponding
curve for Scarlet Fever as represented on graph 3. It
will be observed that the curves are essentially similar in
both diseases, the difference being: —
1. That in Scarlet Fever the smoothing up of the "persons
curve compared with the "house" curve is more marked
2. That whereas in Diphtheria the "persons" and "house
curve both rise in the first month, in Scarlet Fever the
"persons" curve shows a marked rise, and the "house
curve continues to fall.
This rise in the "persons" curve for both diseases in the first
month is due to the influence of previous neighbourhood in
the contraction of the disease. That this was so was definitely
shown in a number of cases, viz.:—out of the 15 cases who
contracted Scarlet Fever within a month of their coining
to the area, in two instances the patient was a return case from
a child discharged from one of the London hospitals. Two
children of the same family fell ill the day they arrived here;
another case was secondary to her sister, who had previously
been removed to hospital in London, and in another case a
visitor gave a child the disease.
In only one case of Diphtheria can this definitely be shown,
this case being removed to hospital the day the family arrived
The difference in the two "house" curves for the first month
may be due to the possibility that the persons from London
who had Scarlet Fever went into houses which had previously
been occupied 'by other tenants, whereas the Diphtheria cases
were admitted to new houses. Actually 4/5ths of the cases of
Diphtheria occurring within one month were persons in new
houses, whereas in Scarlet Fever the proportion was 3 5. It
the difference represented any actual influence of the new houses
as affecting the incidence of Diphtheria, one would liave
expected an unusually large proportion of secondary cases to
occur in these homes, whereas actually, there were no cases
secondary to those cases of either Scarlet Fever or Diphtheria
occurring in the new houses, and only one of Scarlet Fever in
one of the older houses.
Some irregularities on the "house" curve may be expected
to correspond with the irregular rate of building. The maximum
activity occurs in the summer months, resulting in a larger
number of entrants to the Estate at this period. This new
population would thus be present at the time of the increased
prevalence in the following autumn. This occurring each year
there should be by the time of the autumn rise, more persons
who had been here 0-6 months, 12-18 months, etc., than had