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it was possible to fix the onset in the cases : R. H., H. H., W. T., C. A. on 12th October;
S. S. on I8th October ; C. S. on 23rd October ; E. S. on 18th October ; and M. S. on 27th
October. The incubation period is usually shorter than in enterie and may be taken to
be about seven days. The first four cases were infected from a common source during the
first week of October, and from the 12th to the 21st October were in an infectious state
while being up and about part of that period. It may be safely assumed that the second
group of cases were infected from the first four during this period by casual contact.
With regard to the source of infection, milk and the water supply were soon eliminated.
The milk supplied to the institution was from a dairy which also supplied other houses in
the district. There were no cases outside the institution nor in the district from which
the milk came. The water cisterns and supply pipes did not appear to be the subject
of possible contamination. Inquiry into the dietary failed to reveal any likely source
of infection, and this negative result was borne out by the fact that no two patients sat
at the same table. Had the infection come, for example, from tinned meat it would have
seemed feasible that more than one student among the fourteen would be infected from
the portion of food supplied to a particular table. There are 14 tables in the dining hall,
each seating 6, and the first four cases sat far apart from each other in the hall. Were
they infected from food taken outside ? These four were in different years of study and
had only one common ground of association. All four were present at the sports ground
on the 1st October and on the 5th October, three of them taking part in a Rugby game.
It is understood that they had tea there after the matches, and it seems that this was the
only occasion on which they could have been infected from a common source. Dr.
Mackenzie, of the Ministry of Health, made inquiries at the sports ground, but no definite
results were obtained.
Diligent search for a carrier source had meanwhile been made among all those living in
the institution and those attending daily, whether they were students or staff. Some
eight students were kept isolated on suspicion. Bacteriological examination of blood,
faeces and urine were carried out on an extensive scale by Dr. Braxton Hicks, of Westminster
Hospital, and his staff, who spared neither time nor trouble in their diligent search
for bacteriological evidence of a carrier. In some instances examinations were repeated
at every stage. Except for the eight cases which were clinically evident no carrier of paratyphoid
could be traced among the persons concerned with the institution. Only in two
of the eight patients was the bacillus isolated from the blood. Altogether 70 examinations
for the Widal reaction were carried out; specimens of urine and fæces were also
examined by culture and sub-culture.
Beyond what has been indicated above as the possible circumstances of infection, no
further definite evidence came to light. Experience has shown that once paratyphoid
infection has broken out in a residential institution it spreads rapidly, partly because so
many of the cases are so ill-defined, the condition often being put down to a passing chill
or gastric upset. In this instance it would appear that all the eight cases had been infected
before the first case had been notified to this department. The freedom of the institution
from further infection may justifiably be attributed to the prompt diagnosis and removal
of the four secondary cases and the measures of isolation and disinfection which were
carried out. The cordial co-operation of the Principal and his staff were of very great
assistance. Without it it would have been impossible to make the temporary alterations
to the premises whereby a temporary isolation ward was improvised for the close observation
of suspects and a special nurse engaged to look after them. The normal life of the
institution was resumed on the 8th November 18 days after the first notification, or 11
days after the removal of the eighth case.
With regard to the infection of the secondary group of four, it is significant that the
bedroom of one was directly opposite that of one of the primaries. They had washing
facilities in common. Of the two maids in the former group, one was chambermaid to
the room occupied by a primary. These maids were sisters and occupied tho same bedroom.