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Of the 25 cases, 23 were boarders and 2 members of the religious
community, the last 2 falling ill on the 13th and 14th June respectively.
No day scholar suffered in this outbreak and all the child patients were
senior boarders who took their meals in the large dining hall.
Careful inquiry failed to indicate any particular meal or article
of food as the probable vehicle of infection. It was found that a flock
of 31 ducks was kept in the grounds and that the eggs formed part of
the dietary. The only occasion when duck eggs were served whole to
the boarders was on Tuesday, 7th June, the day the school re-assembled,
when the 80 of them had poached eggs for the evening meal. Approximately
80% of the eggs served on that occasion were duck eggs from
the school's own flock, the remainder being hen eggs. This was at
least 40 hours before the onset of the first case and at least 44 hours
before the second case. Duck eggs were served to the boarders
subsequently, but only hard-boiled as part of salads. Samples were
therefore taken from all the available commodities in use which might
have been infected. These were custard powder, semolina powder,
dried egg, dried milk, lard, oxo, water and six duck eggs. These were
all negative for S. typhi-murium as was the culture from the intestine
of one mouse caught in the kitchen.
Attention to the culinary arrangements and kitchen staff revealed
that the kitchen was commodious, well equipped and maintained at
a high standard of cleanliness. Food storage facilities were excellent
and it was with great difficulty that the one mouse was trapped,
evidence of vermin infestation being completely absent. Investigation
of the staff who prepared and handled food elicited two significant facts.
One member of the kitchen staff, W.D., had suffered from sickness
and diarrhoea on the 7th and 8th June, had not reported her illness and
had not gone off duty. Faecal specimens were secured from all the
catering staff and the person, S.J., in charge of the large dining hall
was found to give a positive growth of S. typhi-murium although she
was quite well and had been for several months previously. W.D.'s
specimen was negative—this on the 14th June, seven days after her
onset. In view of the fact that all the cases among the boarders were
girls who took their meals in the large dining hall, the probable route
of infection appeared to have been demonstrated. W.D. and S.J.
were relieved of their food-handliug duties on the 14th June. Strict
hygienic precautions in the washing of hands had already been imposed
on the whole establishment and no further cases occurred for 14 days.
During this interval the use of duck eggs in the dietary of the school
children was discontinued, although they continued to be served to
the religious community.
Phase 2.
On the 28th June a member of the religious community, S.R.,
fell ill with the same symptoms and was followed by two other members
of the community, V.B. and S.A.M., on the following day. Faecal
examination was positive for S. typhi-murium in two of them and
negative in the third. The first negative specimens in the two positive
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