WATER-BORNE EPIDEMICS 541 
Milk-borne Epidemics. The character of this article and the type 
of consumers gives a milk-borne epidemic of infection rather marked 
characteristics. Newman (1904) has mentioned the following: 
(a) There is a special incidence of the disease upon the track of the 
implicated milk supply. It is localized to such area. 
(b) Better class of houses and persons suffer most. 
(c) Milk drinkers are chiefly affected and they suffer most who are 
large consumers of raw milk. 
(d) Women and children suffer most and frequently adults suffer 
proportionately more than children. 
(e) Incubation periods are shortened. 
(f) There is a sudden onset and rapid decline. 
(g) Multiple cases in one house occur simultaneously. 
(hk) Clinically the attacks of the disease are often mild. Contact 
infectivity is reduced and the mortality rate is lower than usual. 
The above characteristics as outlined by Newman (1904) for milk- 
borne epidemics also fit other food epidemics. Sawyer (1914, 1915) 
reported investigations of two typhoid epidemics, one caused by water 
and the other caused by food. Fig. 84 shows the incidence of cases for 
both epidemics. These curves show very well the types which are 
secured for food and water-borne epidemics of typhoid fever. 
Water-borne Epidemics. Such epidemics of disease have been 
common in the past and many such epidemics are described in the liter- 
ature. The important characteristics of such epidemics may be de- 
scribed as follows: 
(a) Water-borne epidemics may be preceded by a period of dysen- 
tery. 
(b) There is usually a slow onset of the epidemic and a rapid decline. 
(c) The cases are evenly distributed over the city if the city is served 
by a municipal supply. 
(d) The larger water-borne epidemics have occurred in the spring. 
Epidemics caused by other foods will show, in general, other char- 
acteristics. If the typhoid fever is caused by oysters, it will be con- 
fined to that part of the year when oysters are usually eaten. Further- 
more, the great majority of the cases will be primary cases—those who 
have partaken of the oysters. To detect carriers may require much 
inferential evidence and the elimination of other suggested causes. 
After this has been done, the indication that a carrier is concerned must 
be supported by bacteriological examinations of the urine and feces of 
the suspected individual. 
