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(3) Pollution during the addition of salt and popper to the hot gelatine
bone stock. The chance of pollution of the salt and pepper during storage
was infinitesimal, but there were opportunities of infection during their
sprinkling, by spoon or sometimes by hand, into the gelatine bone stock.
(4) Pollution during the process of filling the pies with the gelatine bone
stock. Such pollution might arise through contact with the hands of an
infected worker, or by the use of a contaminated funnel through which to
introduce the jelly into the pie. One funnel was reserved for the purpose.
Ordinary care was used in cleansing it, and it was stored loose in a cupboard
containing at the time of inspection an open jar of jam and some confectionery.
The cupboard was easy of access to mice, so that there was a
chance of contamination of the funnel, not only by the hands of the worker,
but also by contact with a rat or mouse sick from the effect of bacterial
virus.
(5) Pollution of flour through infection from sick rats or mice, either
at the flour mills or warehouse, or in the bakery store, or in the service tins
at the bakehouse. The risk of infection seemed remote, owing to the subsequent
heat to which the dough was exposed in the ovens. It was nevertheless
felt worth while to make enquiry of the millers, and of the warehouse
supplying the flour to the Croydon bakery, as to their methods of rat extermination.
No bacterial virus was used by either, nor was there access for
mice to the stored flour at the bakery, except in respect of flour in the service
bins in the bakehouse. These bins had lids, but it was doubtful whether
they were always kept covered when the bakehouse was not in use; and if
not, they were readily accessible to mice running along the tables in the
bakehouse.
(6) Pollution through faulty cleansing of utensils used in the bakery. It
has been already mentioned that the sink in which utensils were washed up
was the only sink in which male employees could wash their hands after
using the lavatory; further, the water used for washing utensils was hot,
but not necessarily boiling, so that there would only be a probability, but
not a certainty, of infecting organisms in the sink being destroyed.
Thus, up to the present stage, while there was left an uneasy feeling
that there was a strong probability of infection by human agency, nevertheless
careful enquiries of each employee at the bakery, and of the antecedents
of others reported by the firm, as well as blood examination of all
the employees at work and of certain temporary employees seen at their
homes, gave no clue to the infecting source. At the same time, definite
suspicion was thrown on chances of pollution during a late stage in the
manufacture of the pies, and in particular on the chance of the gelatine
having been infective, having itself possibly been infected by bacterial rat virus
through the agency of rats or mice in the bakery—this always on the
assumption of the correctness of previous investigations as to the association
between certain bacterial rat viruses and cases of paratyphoid (B) fever, and
the further assumption, which was being subjected to bacteriological tests,
that the bacterial rat virus here used was identical with the bacillus of
paratyphoid (B).
In any case, the trend of the enquiry was to suggest contamination at
the bakery rather than at a branch shop, and to open up the possibility
of cases arising through other hranches, as well as through other types of
confectionery made at the same bakery.
Further evidence of area implicated in outbreak.—At this stage, information
was received in quick succession of some fresh cases of illness, proving
to be paratyphoid (B) fever, where the patient had eaten ham and veal
pies supplied from the central bakery of the same firm to two other
branches. This definitely showed that the infection did not arise in the