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immunity to occur, it is necessary that there should be opportunities for
individuals to receive these small doses of infection, and this can only
happen if the disease is constantly present in the community. If a community
has been free from a disease for many years, the natural immunity
of the individuals will practically disappear, and the re-introduction
of the disease would result in an extensive and very serious
epidemic.
So far as the present state of affairs regarding Diphtheria is concerned,
it can be argued that the infection has not in point of fact
disappeared, but has merely become concealed—that although it is still
present amongst us, the high degree of protection present in the community
prevents the characteristic reaction between parasite and host,
which we recognise as clinical Diphtheria.
I think this view is correct because it would be quite unjustifiable to
assume that the parasite itself had ceased to exist.
The position is, then, that we still have a dangerous disease producing
parasite in our midst, but that our protective measures are
sufficient to hold it in check, and that if we do not maintain our present
high degree of protection, it will inevitably re-assert itself.
There is possibly another factor at work. From bacteriological
work it appears to be true that the repeated passage of a particular
parasite through susceptible hosts, increases its virulence, whilst similar
passage through immune hosts attenuates or weakens it. Whether as
the result of the maintenance of high degree of protection over a number
of years, a marked reduction in the virulence of the parasite will be
achieved remains to be seen. It is safe to say that such a desirable state
of affairs has not yet arrived, because cases of infections by a parasite
with a very high degree of virulence continue to occur in all parts of the
country.
During 1948 a continued effort was made to protect children between
the age of one and two years, and also to give reinforcing doses to children
on reaching the age of 5 years. Up to 30th June, 1948, 433 new cases
completed treatment and 182 old cases had extra doses, compared with
869 and 490 for 1947.
Scarlet Fever.
The number of cases notified during the year was 107, compared
with 54 in 1947.
The incidence was proportionately greatest in the West Wickham
Ward, but cases occurred in all parts of the Borough.
Incidence was fairly evenly spread over the year, the months with
the highest incidence being March and June.
The disease was mild—as it has been for many years now—and there
were no serious complications.
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