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14
It was established that two children had been suffering from a gastrointestinal
upset on the day of their return from holiday, and it is presumed
that they were the original source of the infection.
On the Monday of the following week, that is six days after their return
to school, there were some 66 absentees, the majority of whom had dysenteric
symptoms. The following day the laboratory reported that all the specimens
which had been submitted from suspected cases before the week-end were
positive to Shigella sonnei. Further absences were reported throughout the
rest of the month of May, and each was investigated by the staff of the
department. Some proved to be due to chicken-pox, which was prevalent at the
time, whilst others were kept from school because the parents had heard that
there was an outbreak of dysentery in the school.
The high absentee rate was maintained throughout May. Of 358 on the
roll there were 75 absent on May 7th and 86 on May 21st, though it is not
certain that all of these were true cases of dysentery or positive contacts.
By the end of May there were very few new cases being reported, and by the
25th June there were only 5 known cases to be cleared.
These figures include children who were diagnosed as dysentery on
bacteriological grounds only as well as a few who showed the characteristic
symptoms without returning a positive stool. This latter type of case was
more frequent in the later stages of the epidemic either because it was a
mild infection or one which came to our notice later in the course of the
illness.
An effort was made during the epidemic to obtain faecal specimens from
all family contacts, but this was not wholly successful as the parents did not
fully co-operate.
There were 25 families, however, in which a positive stool was obtained
from individuals whose only contact with the infants' department was through
a child in that part of the school. There were 18 adults (14 mothers, 3
fathers, 1 adult sister) 5 in the junior department of the same school, 5 pre
school children and 5 in other schools. It is interesting to note the high
proportion of mothers anongst the adult positive contacts, although it must be
noted that there were less fathers submitting specimens.
Another interesting feature is the fact that no secondary cases were
reported from the positive contacts attending other schools. These were all
schools for higher age groups.
The almost explosive nature of the outbreak in its early stages suggested
at once the possibility of a food-borne infection originating in some way from
one or other of the first cases. Enquiries showed, however, that only about
two-thirds of the first week's cases had school dinners and in any case the
children had no part in serving the meal.