436 MILK 



"3. The number of invaded houses supplied in whole or in 

 part, directly or indirectly, by the suspected milk. 



"4. The number of cases occurring in invaded houses so sup- 

 plied. 



"5. The number of houses supplied with the suspected milk. 



"6. The relative proportion of houses so supplied to those sup- 

 plied by other dairies. 



"7. The time covered by the epidemic. 



"8. The location of the case or cases from which the milk 

 became contaminated. 



"9. The relation of the original case to the epidemic. 

 "10. The time relation of the original case to the epidemic. 

 "11. The special incidence of the disease among milk drinkers. 

 "12. The elimination of other common carriers of infection. 

 "13. The effect upon the epidemic of closing the dairy or tak- 

 ing such measures as will eliminate the possibility of milk con- 

 tamination from the suspected focus. 



"14. The finding of the specific organism in the milk." 



The cases are marked on a map and a so-called spot-map 

 prepared. A milk-borne can be distinguished from a water-borne 

 epidemic by the fact that in the latter the cases are spread more 

 or less evenly over the whole community, while a milk-borne 

 epidemic is more or less confined to a limited area. This is due 

 to the fact that the water-supply is generally a uniform one 

 throughout a community, while milk is supplied by a number of 

 dealers, and the infection is confined to one dealer or, at most, a 

 small number of dealers. 



After the epidemiologist has found evidence which leads him 

 to suspect a particular milk dealer, he will investigate conditions 

 on the dealer's premises and at the producers' farms. Usually 

 the cause can then be attributed to a diseased person or a carrier. 

 The diagnosis is confirmed by a bacteriologic examination of the 

 sputum, dejecta, urine, or other discharges. The finding of the 

 specific organism clinches the evidence. If the epidemic ceases 

 after exclusion of the suspected supply from the market, the 

 evidence of the culpability of the particular milk-supply is con- 

 sidered complete. 



The prevention of milk-borne epidemics is one of the most 

 difficult tasks of health administration. The larger the com- 

 munity, the more complex is the problem, since the milk is de- 

 rived from a great variety of sources. This might seem an argu- 

 ment in favor of supplies being taken over by large corporations 

 or even by city governments, similar to the method now practised 

 of distributing drinking-water. There are surely many reasons 

 why a single milk-supply controlled by a municipal authority 



