DISEASES COMMUNICABLE IN MILK 77 



discharges from eruptions on the udder. All such infectious matter 

 may be carried to the milk on the hands of uncleanly careless milkers. 



The virus of human disease is contained in the urine and excrement 

 and in the discharges of the mouth, nose and ears of those who have com- 

 municable disease. Epidemiologists distinguish several states in which 

 people may disseminate contagion. There are those in the prodromal 

 stage, that in which the malady is developing in their system. Such 

 people may infect the milk; in typhoid fever, for instance, the victim 

 may eliminate the specific germs for as long as 10 days before the pre- 

 monitory symptoms appear. There are those who are actually sick. 

 They form two groups ; those who are severely ill and so betake themselves 

 to bed and those with mild or walking cases, who feel mean or perhaps only 

 excessively tired so that they do not give up work but continue thereat 

 as usual. Of these two groups both are dangerous but the latter are 

 very much more so than the former for they can hardly avoid infecting 

 the milk if they have to handle it. From this group the "missed" 

 cases arise, cases so very mild that their existence is never detected. 

 They form an important source of communicable disease and at least 

 one widespread milk-borne epidemic has been ascribed to such an origin. 

 Finally there are the carriers of which there are three sorts, the acute, 

 the chronic and the temporary. An acute carrier is one who discharges 

 pathogenic microorganisms for a few weeks after recovery. Such a one, 

 on returning to his duties, may be the cause of an outbreak. The 

 chronic carriers are those who for months or years after recovery harbor 

 and scatter about the germs of the disease that afflicted them. Some- 

 times intermittent chronic carriers are spoken of; the appelation signifies 

 that they discharge the specific germs for a while and then stop doing 

 so only to begin again later. It is only of late years that the existence 

 of carriers has been recognized but they are now and the number of 

 outbreaks that are traced to them increases steadily. The temporary 

 carriers are those who never have had communicable disease themselves 

 but who by contact with those who have, become for a short time dis- 

 tributors of infection. To this class belong those who in nursing the 

 sick infect themselves but do not develop an attack of the disease. 



Finally, contagion is spread by flies that feed on the discharges of 

 the sick and afterward carry the germs on their feet and droppings to 

 milk and other foods. 



Transmission by Milk. Milk may be infected at various stages of 

 its progress from the cow to the consumer, on the farm, in transit, at 

 the city milk plant, in stores, and in the home. The possibilities of 

 infection are taken up in detail. 



Infection of Milk on the Farm. It is conceivable but not probable 

 that cows wading in infected streams might infect their bellies and udders 

 with disease germs that would fall into the pails at milking. No flawless 



