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18
Visiting home contacts of proved cases, the frequency of mild
pharyngitis during the first 10 days was noticed, although this
may well be incidental especially at the time of year under review.
Of a series of 33 cases at Clayponds Isolation Hospital, 9 complained
of sore throat on admission.
Course of the Outbreak.
The main course of the outbreak in Ealing conforms with
that of a simple epidemic although study of the distribution of
cases shows some interesting phenomena.
During August, two main crops of cases occurred at Greenford
and South Ealing, followed in September by an extension in the
South Ealing, Hanwell and Drayton Districts. During October
and November there were fewer cases notified and these were
scattered more uniformly about the Borough.
The remarkable immunity of the residents of the Eastern
wards of the Borough, especially Castle Bar, Hanger Hill, Mount
Park and Grange districts, is shown on the case distribution map
and the table giving the attack rates in the various wards of the
Borough.
The age distribution of cases shows no significant variation
throughout the course of the outbreak.
Mode of Spread.
A detailed field survey was undertaken with a full enquiry
into the home circumstances of each case notified. Apart from
the case of John and Stanley T no definite evidence of more
than one case in a family could be found. Thus close home contact
did not appear to have any direct significance in the occurrence
of secondary cases, although the case distribution map would
indicate that there is spread from case to case, or a common
significant factor causing a relatively high incidence in certain
highly residential areas. No cases occurred among children attending
day nurseries and there was no evidence that attendance at
school affected the spread of the disease.
Abortive cases constitute a problem and illustrate the necessity
for close supervision of contacts of definite cases.
Cases were diagnosed as abortive poliomyelitis on investigation
in the Clayponds Isolation Hospital, the diagnosis being established
on clinical signs supported by examination of the cerebrospinal
fluid. Three cases of slight muscle weakness have been seen by
the consultant orthopaedic surgeon in the school medical department,
probably due to abortive poliomyelitis and these have
rapidly improved under supervision and physiotherapy. The
diagnosis in these cases can be very difficult as there are usually