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31
The importance of flies as a means of conveying infection
more especially in epidemic Enteritis and Typhoid Fever, has
in recent years been remarked upon by several observers,
who have investigated these diseases not only in warm
climates but also in this country.
It has also been shown that the relative dirtiness of
houses is a direct index of the susceptibility of the inhabitants
to Typhoid Fever.
The life history and habits of flies exactly fit in with
the history and cause of this outbreak. It is in July and
August that flies attain to their maximum multiplicity, eating
voraciously and passing indiscriminately from filth collected
in houses, backyards, and streets to various articles of diet in
the house. In the class of house in which the outbreak
occurred, food is left about on the tables long after meals are
over, and little or no care is taken to keep food covered up
and protected from contamination by flies.
It was at the end of August that the outbreak began,
the infection therefore taking place during the earlier and
middle part of the month.
As the autumn days become cooler, flies become less
numerous. They lose vitality and seek shelter in the warmest
places available, and cease to settle alternately on refuse
matter and articles of food, and by the end of November
disappear altogether.
In like manner the number of notifications, after increasing
throughout September, which was fine and warm, began
to decline in October, and throughout that month and
November, until during the week ended December 1st they
had ceased altogether.
(V.) Direct and Indirect Personal Infection.—The
class of persons inhabiting the infected area are of the poorer
working classes, for the most part dirty in their habits and
houses, and with a somewhat high average number of
persons per house compared with the rest of the district.
They are frequently in and out of each other's houses, thus
favouring direct and indirect infection. They are of a class
who take little notice of illness and indisposition until it
assumes an acute form, and who do not think much about the
possibility of any illness being an infectious one unless accompanied
by a marked and obvious rash. Nor are they likely
to concern themselves or exercise much intelligence about
taking steps to prevent the spread of an infectious disease