View report page

50
Scarlet fever is one of the diseases which has seemed to have a long
cycle of 20 to 30 years. Superimposed on this is a short cycle of 4 to 6
years, while, typically the seasonal incidence is shown as an increase
throughout the summer to a maximum to October or November, falling
from December to a minimum in March or April. For the country as a
whole from 1919 to 1933, the incidence ranged from 2.05 to 3.65 per
1,000 population. The typical periodicity is more likely to be found in
stable communities, and less likely in such a district as this, where for
the pre.war years there was a steady importation of a new population,
and during the war, apart from evacuation, a movement of the population
occurred on a very large scale. Local rates then have ranged from 1 .06
to as much as 4.70 per 1,000 population. Such fluctuations in the incidence
of the infection in a community in which other factors do not
change much from year to year, except the degree of immunity which
quite possibly will be dependent on the preceding incidence of infection,
are probably, then, the result of changes in the organism responsible
for the disease. If the organism can change in its power of invasiveness
in this way, there must always be the risk that it can change its virulence.
Scarlet fever has in a few decades changed from being a dread disease
with a high case mortality to one which is so mild that there is a danger
of its being treated too lightly. A few hold that admission to hospital
of the more serious cases resulted in the organism at large becoming less
virulent. Others see in the reduction of the severity at the same time
of scarlet fever, measles and whooping cough, the result of some common
factor which might be one such as the better nutritional state of the
general population. On the other hand, it could easily be pure coincidence
that the virulence of the causative organisms of these three infections
should about the same time have diminished. If so, then
presumably there is always the possibility of a reverse change with
increasing seriousness of the infection of those affected.
Since the high incidence of 1943 when there were 672 cases, an attack
rate of 3.52 per 1,000 population, this district has not been severely
attacked, and in general has escaped more lightly than the rest of the
country. For instance in 1948 there were under 200 cases, an incidence
rate per 1,000 population of 0.82, which was something less than half the
figure of 1.72, the rate for the country as a whole. For much of 1949 it
seemed that the district was again to be only lightly affected, but the rise
in the late months was quite marked ; this was in keeping with the
national rate.
Another change in the behaviour of scarlet fever locally is that this
year as a marked contrast with what has occurred in previous years,
there appears to have been more grouping of cases amongst the children
attending the same school.
During the year, 360 cases were notified as suffering from scarlet
fever. In nine of these the diagnosis was subsequently amended, the
corrected number of cases being, therefore, 351, or an incidence per
1,000 population of 1.60. The figure of incidence in the country as a
whole was 1.63.