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55
Secondary Infection.
There were 20 households in which a secondary infection
followed on the first case. In 15 instances only one further case
occurred; in three households two further cases followed, and three
and four cases occurred on one occasion, making a total of 28
secondary infections.
In no instance did a secondary infection occur in a household
in which the original patient was treated at home after the diagnosis
had been made in the first case, though there were four instances
in which secondary infections had occurred in a home treated case.
In two instances the diagnosis of infection was made in the second
case at the same time as it was made in the case of the original
patient. In one the recognition of the disease in the secondary
case led to the detection of the disease which had been missed in the
first case. In the other instances two members of the same family
succumbed the day after the diagnosis had been made in the
primary patient. 111 patients were treated at home without the
occurrence of secondary cases.
In most cases where secondary infection had occurred the
onset followed soon after the onset in the primary case. Of the
20 cases (where more than one was secondarily infected only the
first of these cases is being considered) the time separating the
onsets was one day in three instances, two days in six, three days
in one, four days in three. In one instance in each case, the number
of days interval was five, six, seven, nine, thirteen, fourteen and
eighteen. These latter cases are all instances of missed cases where
the disease was no, recognised in the first patient until at a later
stage.
Of the 16 cases in which a secondary infection occurred in a
home from which the primary patient was removed to hospital,
in nine the onset of the disease in the secondary patient preceded
the removal of the primary patient, in many instances the diagnosis
being made in both at the same time, and the patients being removed
to hospital together. In a further three instances the onset of the
illness of the secondary case was the same day as the primary
patient was removed. The interval separating the onset of illness
in the secondary from the time of the removal of the primary case
was, in the remaining four instances, two, three, four and ten days.
Of the households where there was more than one secondary
case, in the instance where there were three such secondary
infections, all succumbed the same day, which was the day preceding
the removal of the primary patient. In one of the cases
where there were two secondaries, these had a simultaneous onset
the day following the removal of the first case. In the other
households where there were two secondaries, the intervals
separating their onsets were two and three days. In the house
where there were four secondaries, the onset and removal to
hospital of the first preceded the diagnosis of the disease and