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possible the disinfection and preparation. of the patient is now
carried out some days before the day of discharge.
Although a better classification and a more satisfactory system
of preparation before discharge will greatly reduce the number of
"return" cases, it is doubtful if they will entirely disappear. The
wider recognition of the occurrence of return cases has been the
means of raising other questions. One of these relates to the length
of time during which a person attacked by Scarlet Fever may be
infectious, and in this connection it is of interest to note the liability
of cases to recur in families after a prolonged period.
Last year Scarlet Fever cases occurred in 376 houses, and
during the last three years 708 houses have been invaded.
There are over 9,000 inhabited dwelling houses in the district.
During the year recurrent cases occurred in 90 houses. 43 of these
houses came under group 1, where the secondary case occurred within
the month of the removal of the previous case to Hospital; in 27 of
the houses the cases came under group 2—the "return" cases
referred to on a previous page, and the remainder, 20, referred to
houses from which a recurrent case was notified after a lengthened
period had elapsed, and the interval which elapsed between the first
and second case was as follows :—
6 weeks 1 case
7 ,, 2 cases
11 ,, 1 case
4 months 2 cases
5 ,, 3 ,,
10 „ 2 „
11 months 1 case
17 ,, 1 ,,
18 ,, 1 ,,
23 ,, 2 cases
24 ,, 2 ,,
27 „ 1 case
It is impossible to state accurately what are the chances of a
second case occurring in a house, apart from contact and return
cases.
There are many factors which operate, the most important
depending upon the number of susceptible persons in the houses, and
the chances of infection in school.
Numerically, the last group does not seem very important, but
taken in conjunction with the return cases, it may repay analysing,
as some light may be thrown on the epidemiology of the disease.