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spread, namely, the 0-1 year and the 1-3 years groups, constituted
only 13% of the total cases notified. Certainly experience in Greenwich
over the past 5 years seems to confirm this view, for in no outbreak
investigated during that time has food or drink been seriously
indicted. If, in fact, it is true that the disease has undergone a
fundamental change in natural history, the method of control will
have to be varied. With this apparent change in mode of spread
seems to have come an increase in infectivity and the new method
of spread is more effective. This would account to some extent
for the remarkable increase in incidence.
It was with these thoughts in mind that we decided to try to
analyse the information which we have collected in our investigations
; in particular we have classified the primary and secondary
cases according to age and sex, and we have tried to relate the secondary
spread to environmental and social factors in respect of occupation,
density, size of family and ablutionary facilities. In regard to
the latter, in some cases we have had to draw certain inferences from
the collective knowledge of the Borough of members of the staff.
The outbreak began explosively in February and increased in
incidence through March with peaks in April, May and June; thereafter,
as will be seen from the accompanying graph, there was a
gradual defervescence and there was no autumnal recrudescence.
The procedure of investigation was as follows : all notified
cases were visited and faecal specimens taken from the patient and
all other members of the family. Positive cases were referred to
their private practitioners for treatment and faecal specimens taken
at weekly intervals until two consecutive negatives were obtained.
Time and shortage of staff precluded our insisting on three consecutive
negatives. Positive excretors were excluded from school and
from work involving handling or preparation of food, until two consecutive
negatives were obtained. Refractory cases were given
special attention and single drugs and combination of drugs were
tried. Talble I shows the number of primary and secondary cases
classified according to age and sex.
It will be seen that in accordance with general experience in
the country, the 5-15 age group predominates, accounting for 48%
of total notifications. This contrasts with our experience of 1951
when this same age group accounted for 25%. With the apparent
change in method of spread there has been a change in age group
incidence. It may be that this can be accounted for by the greater
mobility and more diverse activity of this group. Undoubtedly,
the schools seemed to be the main source of primary infection, for
school children accounted for 53% of the total number of primary