544 EPIDEMIOLOGY 
Determination of the Origin of an Epidemic. In the majority of 
epidemics, the foci may be discovered with a fair degree of accuracy. 
Hill (1912) has given the detailed procedure and part of his paper is 
reproduced below. On account of the standing of this authority in this 
field, the author feels justified in quoting rather extensively from his 
work. In the last analysis, the epidemiologist must be a many-sided 
man; he must be somewhat of a bacteriologist, psychologist, and 
detective. He must have the intuition to separate the essential from 
the non-essential data. Then, somewhat like the lawyer, he should have 
studied reported epidemics in order to determine how others have been 
investigated. 
“To illustrate the general principles, let us suppose notification 
be received that a typhoid fever outbreak exists in a far-off community. 
The public health detective packs his grip and goes. He knows no 
details; he has never heard of this particular community before; he 
has not even any general information about the character of the country; 
he enters the community with no preconceived ideas. But he does know 
how typhoid fever originates and how it spreads. Water, milk, food, 
flies, and fingers are the routes—typhoid cases or typhoid carriers the 
source. His duties are to find both; and to find them, not as a scien- 
tific amusement, or as a matter of record; not to furnish food for spec- 
ulation—above all not to make a show of doing something—but to 
stop the outbreak; and then to advise measures to prevent recurrence. 
“The public health detective on entering the community affected 
by typhoid fever does not first examine the water supply, the milk sup- 
ply, the sewage disposal system, the markets, the back alleys, the 
dairies or anything else. He goes directly to the bedsides of the patients. 
Of course he must obtain the names and addresses of the patients 
from someone—from the local health officer, if he has them; from the 
attending physicians, if the health officer has no list; from the lay citi- 
zens themselves, if no one else is immediately available. The more 
complete the list, the faster he can work, because then he is not com- 
pelled to hunt up the cases personally. But if there be no list, he 
begins making one himself. His intention is to see just as many patients 
as he can, for each furnishes evidence and he wants it all. But he knows 
that it is not always necessary at this stage to see absolutely all the 
patients, so long as he sees the majority. 
‘Reaching the patient’s * bedside, his investigation begins. Auto- 
* Tf the patient is a child or delirious or not strong enough for an interview, or 
speaks only some foreign tongue, the relatives, friends or associates must supply the 
information. 
