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In later life there are a few rarer diseases which attack people after the age
of about 40, such as psittacosis (parrot disease) and encephalitis. At still more
advanced ages the human body loses the power of resisting attacks of all
micro-organisms, so that in old age the terminal event is often caused by a
comparatively minor infection which at a younger age would have caused little
or no inconvenience.
Antibiotics.
Over the last 20 years or so there have been discovered a number of drugs
and chemical compounds which have astonishing efficiency in curing many
human microbial infections and in controlling numerous pest diseases in humans,
animals and plants. Examples are the sulpha drugs, penicillin, aureomycin,
DDT, and the organic phosphorus compounds. It is supposed that in human
infections, the chemotherapeutic agent strikes at one or more of the enzymes
present in the body of the organism and necessary for its survival and propagation.
Most of the common organisms can, by gene mutation, enable succeeding
generations to acquire resistance to the healing drug. This is of little importance
in the case of one individual patient; but a danger would arise if a large
proportion of individuals at risk were partially protected, or where most of the
reservoirs or sources of the infection were being treated. There might thus
arise new species of organisms with greatly enhanced virulence which would not
respond to any of the known drugs in current use. Suppose, for instance, a drug
was discovered which affected one small part of the vital processes of the
tuberculosis bacillus, and suppose the drug were given to all known cases of
tuberculosis, it might happen that the descendants of the bacillus would acquire
a resistance to the drug and a greatly increased power of attack, not only
against those people already infected, but also against those—the rest of the
population—who have already acquired a comparative immunity against the
non-virulent strain. It is important therefore that research be continued to
discover drugs which have a deleterious effect on the vital processes of the
bacteria in a number of ways, so that if one remedy proves ineffective another
can be used; the danger of spread of drug-resistant variants would thus be
minimised and there would be no argument for withholding treatment from any
individual for fear of creating resistance strains of organisms.
The thought here is that the warfare amongst species—from bacteria to
human beings—is constantly being waged; it is the fittest who survive ; and
we must be constantly on guard.
TRACING CONTACTS
The control of infectious diseases sometimes calls for exhaustive enquiries
and often occasions visits at week-ends and in the evenings to persons who have
been in contact with major infections such as smallpox and typhoid. A large
number of these contacts are persons who have recently returned from abroad.
The tracing of such contacts is vital. It must be carried out unobtrusively
and with painstaking care, and moreover must be done speedily as in these days
of travel, a person can move from a tropical country to residence in Twickenham
in a matter of two days. If such a person is an infected contact he may show no
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