88 CITY MILK SUPPLY 



Milk-borne epidemics follow the delivery wagon. This is most 

 plainly seen in small routes supplied from a very few farms; in large 

 routes where all the milk is not mixed together the connection between 

 milk delivery and contagion may be less obvious, but usually patient 

 inquiry at the dairy and along the route will develop such a relationship 

 if it actually exists. 



Great care must be taken not to unjustly impute an epidemic to a 

 milk supply. The mere fact that the number of cases is large, while 

 sufficient to arouse suspicion, does not warrant the conclusion that the 

 supply is actually responsible for an outbreak. The percentage that 

 the milk served by the suspected dairy forms of all milk in the district 

 under scrutiny must be determined, as well as the number of cases on 

 the route. A dairyman who serves 50 per cent, of the families in a dis- 

 trict may be expected to have among his customers a large number of 

 cases of a contagion that breaks out therein. Harrington instances an 

 outbreak of scarlet fever in Boston in 1897 that was wrongfully attributed 

 by the public to a milk dealer who delivered to most of the stricken families. 

 Careful investigation by the health department showed that the first case 

 was that of a child who did not have the accused milk and that the epi- 

 demic was spread by contact from this first case. Pease tells of an epi- 

 demic where 50 per cent, of the cases were customers of a single milk dealer 

 who was forthwith accused of causing the outbreak but who was cleared 

 of responsibility, upon it being shown that an infected water supply 

 was really to blame, it being simply a coincidence that the dealer supplied 

 50 per cent, of the cases. 



In milk-borne epidemics it so often happens that more than one case 

 appears at the same time in a single household that such occurrences 

 warrant the suspicion that the milk supply may be involved. 



It frequently happens also, that the better-class houses are invaded 

 for the reason that the occupants can best afford milk and so use it more 

 freely than do the poorer classes. Those households using the most milk 

 are most frequently attacked and show the greatest percentage of cases. 



Likewise, there is a special incidence among milk drinkers; often a 

 member of a household who abhors milk will escape infection, whereas 

 those that drink milk freely are attacked. 



The age and sex of the victims is frequently indicative that milk is 

 responsible for an outbreak. If the sufferers are mostly women, young 

 people and children, the epidemic is likely to prove to be milk-borne, 

 for they consume milk more freely than adult males. Judgment must 

 be exercised in applying this rule, for in some communities children form 

 a considerable part of the population while in others they are conspicu- 

 ously absent. 



As to the character of milk-borne outbreaks there is some evidence 

 to indicate that the infections may be more benign than when they origi- 



