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noting that four individuals each had two separate attacks of the
disease during the twelve months.
There were 240 Primary cases : in 18 homes there was more
than one case : in all there were 21 Secondary cases.
Of the secondary cases, eleven were classed as " Return "
cases (i.e., cases which developed in a house within three weeks
after the primary cases returned home from hospital); eight
cases occurred within four days after the notifications of the primary
cases in their homes ; and two cases did not occur until more than
four weeks after the notification of the primary cases.
Of the 261 cases, 151 were removed to the Isolation Hospital,
and 110 were treated in their own homes.
In the 151 homes whence the cases were removed to hospital,
there were 147 contacts between the ages of 9 months and 15 years
who had not had the disease: in the 110 homes where the cases
ware treated at home, there were 57 contacts of similar ages who
had not had the disease.
The table shows the percentage of the above mentioned
contacts in each group (a) who developed the disease within four
days of the primary case and (b) who developed the disease at least
four weeks after the primary case.
Hospital cases. Cases treated at home.
Within four days 3.4% 3.5%
After four weeks 7.4% 5.2%
This suggests that the risks of early secondary cases is the same
whether the primary case is removed to hospital or not (and this
is not surprising, because the patient is probably most infectious
in the early stages before the diagnosis is established) : with regard
to the late secondaries (cases which occur after the original case has
returned from hospital, or has been released from isolation at home)
there is a slight but definitely greater risk in the homes where the
original case was removed to hospital. The probable reason is that
cases who go to hospital have opportunities of becoming infected
with strains of the infecting organism other than the one which
caused the original attack, and can thus introduce an entirely new
infective agent into their homes on their return : whilst those who
remain at home are not subjected to this risk. If the contacts of
the home treated case do not get infected before the original case
is isolated, there is less chance of their becoming infected with the
same organism at a later, stage, than there is of their becoming
infected by an organism of a different strain.
This does not imply that there is any lack of care by the staff
of the Infectious Diseases Hospital in discharging cases : cases may
be perfectly free from infection on discharge, but owing to an
attack of simple catarrh of the nose and throat, may again become
infectious. This is a well-known risk and cannot be avoided : in
the series of cases under review it happened in just over 8% of the
cases—a figure which is rather higher than is generally found.
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