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72
SCARLET FEVER.
During the last two years Scarlet Fever has prevailed in much
greater degree than during the years immediately preceding. There
were notified altogether 641 cases during the year, actually the
highest number hitherto notified, and giving a scarlet fever incidence
rate of 4.4 per 1,000 as compared with a mean rate for the last
20 years of 4.0 per 1,000. Rut for the adequate provision of hospital
isolation, it is certain that the prevalence would have assumed the
proportions of an epidemic.
On page 63 will be seen a map on which the cases of scarlet
fever occurring during the last 5 years are spotted. The cases are
distributed equally along the streets in which they occur. Upon comparison
with a similar chart showing similarly the distribution of
Diphtheria and published in my last Annual Report, a marked contrast
will be observed. Whereas diphtheria shows a preference, so to
speak, for certain areas where it appears to luxuriate, irrespective of
the density of population of the area, scarlet fever is more uniformly
distributed according to the density of population upon area. The
map may be described as roughly indicating a distribution of scarlet
fever in which the cases are numerous directly in proportion as the
population is denser upon area. Whether this would hold true of a
larger survey it would be unsafe to infer in the absence of more
direct knowledge.
THE PERIOD OF INFECTIOUSNESS IN SCARLET FEVER.
The wider recognition of the occurrence of return cases of scarlet
fever has raised the question of the duration of infectiousness in
persons attacked to one of the first importance in connection with
this disease. With a view to throwing some light upon this problem
I have gone through the records of the past 8 years and abstracted
and tabulated all the cases of houses in respect of which multiple
cases of scarlet fever were notified as occurring at intervals of from a