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8
1.—There is presumptive evidence of a direct case-to-case
spread and close contact with a patient incubating the
disease and harbouring the virus can lead to infection.
2.—There is apparently a carrier state.
3.—It is unusual for more than one member of the one family
to contract poliomyelitis in detectable form. (However,
in the present series 2 members of one family contracted
the disease. The paralytic case in this instance was
followed by the non-paralytic within the space of one
or two days).
4.—Members of a family, where there is a case of poliomyelitis,
may be harbouring the virus and can contribute to the
spread of the disease.
5.—There seems to be wide variation in degree of susceptibility
and immunity.
I make no claim that these observations are in any way original
but they seem to bear out the theory of the possibility of spread by
carrier and by droplet infection. In other words, poliomyelitis
behaves like many other infectious diseases but with additional
puzzling aberrations in regard to virulence, infectiousness, viability
of the virus and individual immunity and reaction to infection.
Outbreaks seem to differ in the method of dissemination, some
apparently being by droplet spread, others by the gastro-intestinal
route and both methods may be operative simultaneously.
Unfortunately, the virus was never recovered nor, indeed,
looked for in the close contacts. It is a difficult task to organise
with the limited staff available and it is to be borne in mind that
the poliomyelitis virus is not so easily isolated nor identified as the
diphtheria bacillus from the throat or the typhoid bacillus from the
bowel of carriers, and its detection and growth require highly
specialised techniques for which suitable laboratory facilities are
limited. Never tireless, some effort in the future will have to be
made to obtain some precise information about those abortive cases
who may betray no signs of clinical poliomyelitis but who are
infected, and also those who may have been previously infected and
have shown no demonstrable sign of illness and who have acquired
an immunity and may be acting as carriers.
As yet we know very little of defence mechanisms and practically
nothing about the carrier state and how long a person harbouring
the virus can remain potentially infective. It is only by
extensive mass observation in times of increased prevalence that we
may glean sufficient knowledge to enable effective preventive
measures to be taken.