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Observation during the last two years lends support to the view
that late secondary cases are commoner in houses where the original
case was removed to Hospital than in houses in which the first case
was treated at home. It is possible that in the latter instance
the other occupants of the house, though not in actual personal
contact with the patient, acquire a reasonable degree of immunity
against the disease.
POLIO-MYELITIS AND POLIO-ENCEPHALITIS.
These titles probably refer to a single disease, the description
varying with the part of the central nervous system principally
affected in each case. The more generally known name of this
disease is Infantile Paralysis.
The epidemiology of the disease is not fully understood. It
principally affects young children and adolescents. It is more prone
to occur in the late summer and autumn. It is noticed that it tends
to break out at the same time in many different areas all over the
country ; or even all over the continent ; this tendency appears
to be commoner with diseases caused by a virus, than in diseases
caused by demonstrable bacteria. The infection is believed to gain
access to the human body through the upper respiratory passages,
and present opinion regards the terminal filaments of the olfactory
nerves in the roof of the nasal passages as the point of entry. The
infection appears to involve the central nervous system by direct
extension along the nerves themselves ; it is not, primarily at any
rate, a blood borne infection. This may explain why the use of
antitoxins have proved to be of no practical assistance in preventing
infection or combating the disease. On the other hand, the relatively
low incidence among adults suggests that most people are able, in
the course of time, to acquire an adequate degree of natural active
immunity. The disease is thought to be due to a virus, and is spread
by " droplet " infection in much the same way as the ordinary
common cold spreads. No information of practical value can be
obtained from swabs taken from the throats or noses of patients or
contacts, and this in itself adds considerably to the difficulties of
controlling an outbreak. If one adds to this the fact that in every
outbreak, mild and abortive (but still infectious) cases are extremely
common, the difficulties of control are apparent. Recent opinion
suggests that very little reliance can be placed on ordinary douching
or spraying of the nasal passages as a measure of prophylaxis ;
though work is proceeding in America on the possible value of
spraying the roof of the nose with certain substances. Initial
reports on this process are encouraging, but it requires a much more
extended period of trial; it is, however, already quite clear that the
work requires the employment of a special technique by surgeons
experienced in throat and nose work.
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