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43.
The most painstaking investigations were made to
ascertain the cause of the outbreak. The inquiries were
made in conjunction with the Medical Officers of the
Ministry of Health and the London County Council,
more especially Dr. Macewen of the Ministry and Dr.
Brincker of the County Council.
The questions of water supply and foods naturally
received special attention. Many other agencies such as
Hies have also been considered. The possibility of the
water of the public baths being responsible was also
enquired into.
The evidence pointed strongly to infected cream as
the main cause of the outbreak. In a considerable
number of the cases cream had been consumed bv the
patients approximately 10 to 14 days before the onset
of their symptoms. This period corresponds to the incubation
period of the disease, that is to say, if infected
food material is consumed the patient has no symptoms
until 10 to 14 days have elapsed.
Source of Infection.
The enquiries showed that the cream consumed by
the patients was supplied in a considerable number of
the cases to retail dairymen by one wholesale dairy firm
trading in London. In some of the cases there was no
definite evidence that cream was consumed but milk had
been consumed which was from the same source which
we may call X for the purpose of description.
1 he evidence collected by the Ministry of Health
and the London County Council in relation to the whole
outbreak left no doubt that the medium of infection was
the cream supplied by the wholesaler X. The cream on
being subjected to bacteriological examination by the
London County Council was found to contain Bacillus
Coli in sufficient numbers to show contamination but
paratyphoid bacilli were not found.