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15
The number of cases notified increased gradually, week by week, from
the second week in April, until the fourth week in June. The number then
rapidly increased until the maximum was reached in the first week in October,
when 128 cases were notified. From that time onwards the number decreased
weekly, until the Christmas week, when there was a temporary rise.
The propagation of Scarlet Fever is dependent upon a specific contagium
derived from a previous case of the disease. The incubation period (the time
elapsing from the infection to the appearance of any symptoms), varies from
a few hours to eight days, and is usually from twenty-four hours to three
days. It is most infectious during the acute stage of the fever, when the
sore throat and rash are most highly developed. It used to be considered
that Scarlet Fever was infectious so long as the peeling of the skin lasted.
It is now believed that the latter has nothing to do with the spreading of
the disease, but that the patient may remain in an infectious condition for a
long time, if there is discharge from the nose or ears. The contagium clings
to clothes, bedding, and furniture of the sick room, but is not capable of
diffusion and dissemination through the air without loss of virulence.
The usual duration of infectiveness has been considered to be from six
to eight weeks. The patients are, however, often discharged from the Hospitals
of the Metropolitan Asylums Board in a month and under, if there is no
discharge from the nose and ears, even if there is profuse peeling of the skin.
In most instances where a second case is reported to me, immediately
after the return of the patient from the Fever Hospital, it is found that the
first patient has a discharge from the nose or ears, which has possibly developed
within a few hours of leaving the Hospital. Four such "returned" cases
occurred last year, and the facts were reported to the Metropolitan Asylums
Board.
Scarlet Fever epidemics tend to recur every few years, as a fresh series
of susceptible children become exposed to contagion. The liability of the
unprotected to attack is small in the first year of life, increases to a maximum
in the fourth or fifth year, and then becomes rapidly smaller and smaller with
the advance of years.
The chance that an attack will terminate fatally is highest in infancy, and
diminishes rapidly year by year afterwards. The longer, therefore, an attack
is deferred, the less likely is it to occur at all, and even if it occurs eventually,
the less likely is it to end fatally.