72 MILK AND THE PUBLIC HEALTH chap. 



B. Indirect human infection. 



C. Infection of bovine origin whether direct or indirect. 

 Direct Huvian Infection. — Milk may become directly 



infected from a person either suffering from infectious disease, 

 or carrying the infective organisms. Of these ways, the 

 following are the most important : — 



{a) One of the commonest sources of infection is that 

 amongst the milkers, or others handling the milk, one or more 

 are suffering from the infectious disease in a mild and hitherto 

 unrecognised condition. Occasionally, it has not been officially 

 recognised because of culpable carelessness on the part of the 

 sufferer or his employer. 



(V) A second common source of infection is from persons 

 who are brought into contact with sufferers from infectious 

 disease being employed handling cows, milk, or milk vessels. 

 In many epidemics the origin of the outbreak is to be traced 

 to infectious disease in the family of the cowman or milk 

 distributor. The sufferers are not properly isolated, and the in- 

 fective organisms are carried into the milk on the hands or cloth- 

 ing of the members of the family connected with the milk supply. 



(c) Sometimes no person actively suffering from infectious 

 disease can be found in any way connected with the milk 

 supply, and the source of infection has been found to be 

 a person who, while exhibiting no signs of illness, yet carries 

 the germs of the infectious disease in the throat, nose, or 

 other part of his body. The recognition of such carrier cases 

 is a comparatively recent triumph of preventive medicine, and 

 this source of infection is one of great importance. 



Allied to these cases is the small group of outbreaks due 

 to infection from persons who have not handled milk while 

 suffering from infectious disease, but who have returned to 

 work apparently cured although still in an infectious con- 

 dition. 



Indirect Human Infection. — In a considerable number of 

 milk-borne outbreaks, particularly of typhoid fever, the source 

 of infection has been indirect, and usually from infected water. 

 The opportunities for such infection are not uncommon, 

 although less operative to-day now that typhoid fever is a 

 comparatively rare disease. 



As detailed in Chapter XV. it is still common for milk 



