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spectacular results have not been obtained, although definite progress
has been and is still being made.
Several theories which were previously held have now been
discarded, by a process of very careful elimination. A good deal
more is now known about the virus which causes poliomyelitis.
We are also coming to believe that the spread of poliomyelitis is by
restricted channels, rather than by the presence in the population of
a comparatively larger number of potentially dangerous "carriers."
In other words, our previous idea that every clinical case of poliomyelitis
which was definitely confirmed represented a vast number
of incidents so mild as to pass unnoticed, is being revised. This
latter theory is still held in certain quarters, although the evidence
now tends to show that spread is along definite often detectable
routes.
It is quite possible that non-detected "carriers" still play a
part in the spread of poliomyelitis ; it is equally clear that discovery
of the means by which individual cases are infected is seldom easy,
especially during those periods when few cases are occurring. If
one could definitely state that any given case were the first in a
series, and if this information were obtainable at a sufficiently early
stage, detection of the route by which infection is spread would be
much more simple. Uufortunately, although every case is very
carefully investigated, this vital information is seldom available.
Claims have been made by United States workers that there
are now reasonable hopes of an effective vaccine against poliomyelitis
being available in the relatively near future. If and when
this vaccine does become available, we may look forward to the day
when protection against poliomyelitis can be achieved along the
lines which have proved so successful in the case of diphtheria.
A certain degree of protection has also been obtained by the
use of gamma globulin, a fraction of blood plasma which has
proved useful in the past in controlling outbreaks of measles in
closed communities such as day nurseries and the like. It will be
realised that these safeguards are not yet available. For the
moment, therefore, we must continue to rely on more general
measures, particularly the safeguards which lie in the practice of
strict personal hygiene and the surveillance of contacts.
As reported in my Annual Report for 1952, we carried
out certain investigations into the possible spread of the poliomyelitis
virus in sewage at the request of the Central Public Health
Laboratory. These investigations did not yield positive results, and
have now been discontinued. This is merely one example of the
many types of investigation which are being carried on and which
will doubtless be continued. The fact that an investigation of this
character is negative does not lessen its importance. Few if any
discoveries of real significance have been made without a prolonged
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