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At the home . — Milk after being delivered to the house may become 
contaminated by the hands of those caring for the sick or by flies, 
etc., and be the medium of conveyance of infection to other members 
of the household. 
DETERMINATION OF AN OUTBREAK OF TYPHOID FEVER DUE TO 
INFECTED MILK. 
In the epidemiological studies of typhoid fever in a city a card 
should be kept for each milk dealer and on this card should be noted 
all cases of typhoid fever in persons who within thirty days previous 
to onset of illness have used milk supplied by that dealer. Thus, as 
soon as an unusual number of cases are reported along the route of 
any dairyman it is apparent on the card and attention may be given 
at once to the dairy and the farms supplying the dairy with milk. 
A number of conditions should be taken into consideration in 
determining what constitutes an unusual number of cases among the 
customers of a given dairyman. Of those conditions to be especially 
considered are the general prevalence of typhoid fever in the com- 
munity, the amount of milk sold, the method of handling the milk 
at the dairy, the number of sources from which the milk comes to 
the dairy, and the way in which milk is served to customers. 
Ten or fifteen cases occurring in the course of ten days among 
the customers of a dairyman who sold 1.000 gallons of milk daily, 
and who at his dairy mixed the milk received from the various 
dairy farms supplying him before delivering it to his customers, 
might not impress an investigator as being an unusual number of 
cases, especially if typhoid fever was generally quite prevalent in 
the community and the cases among the dairyman’s customers were 
distributed over a large section of the city. On the other hand, if it 
were learned that at the dairy the milk was bottled directly from 
the individual cans as they came from the different farms, and that 
the 10 or 15 cases had occurred among persons who had been served 
with milk from one farm which supplied the dairy with 10 or 20 
gallons of milk daily, suspicion would fall at once upon the milk. 
In the first case, however, the milk might have been equally at 
fault, the infection having been originally in one can of milk as it 
came from the farm; but as the milk in this can was mixed with a 
large volume of other milk in which, due to temperature, lack of time, 
or other conditions, the infective organisms did not undergo much 
multiplication, and so were distributed in high dilution in the milk, 
even as they may be at times in cases of water infection. 
In order to properly charge to each dairyman the cases having 
used milk supplied by him it is necessary to take into consideration 
not only the source of the milk used regularly by the patient during 
