90 BACTERIOLOGY FOR NURSES j 



milk is supplied cases of infantile diarrhea are of much less fre- 

 quent occurrence. 



Typhoid Fever. The typhoid bacillus is the cause of more 

 milk-borne epidemics than any other organism ; yet it is seldom 

 that it can be isolated. Generally, however, examination of the 

 feces of the employees handling the milk reveals a convalescent 

 case or a " carrier." In some cases infection has been traced to 

 the use of contaminated water for washing the milk utensils. In 

 Washington during the four years 1907-1910 10 per cent of all 

 the cases of typhoid fever were traced to milk. 1 



Scarlet Fever. Although the organism causing scarlet fever 

 is as yet unknown many epidemics have occurred, presumably 

 due to milk infected from human sources. 



Diphtheria. Milk-borne epidemics of diphtheria are less fre- 

 quent than those of typhoid or scarlet fever. The source is 

 generally a convalescent case or a carrier. 



General Character of Milk-borne Epidemics. An explosive 

 onset and a gradual decline generally indicate a contaminated 

 milk or water supply. If the bacteria in the milk are compara- 

 tively few the disease may only appear in a few susceptible persons 

 who drink it; if the organisms are numerous the infection may 

 be carried along the entire milk route. At first the disease appears 

 only amongst those who have partaken of the infected milk ; later, 

 secondary cases may appear. 



Sterilization of Milk. With the realization of the possibility 

 of disease-producing organisms being present in milk the question 

 arises as to the best method of destroying them and rendering 

 the milk safe as a food. Sterilization by heat is the only practical 

 method. Boiling, however, is objected to by pediatricians on the 

 ground that cases of scurvy and rickets are likely to develop in 

 infants fed exclusively on boiled milk. Fortunately these dangers 

 can be obviated if instead of being boiled the milk is pasteurized. 



Pasteurization. The process devised by Pasteur for preserv- 

 ing wines without loss of their original flavor is found to be equally 

 well adapted for the treatment of milk. As the object of pasteur- 

 1 Rosenau, "Preventive Medicine and Hygiene," p. 574. 



