80 MILK AND THE PUBLIC HEALTH CHAP. 



number of milk-borne typhoid fever outbreaks are never 

 reported at all,, or ' only recorded in the annual reports of 

 medical officers of health, and as such not readily accessible. 



The importance of milk as a vehicle for the spread of 

 enteric fever has been greatly underestimated. As an illustra- 

 tion of its importance it may be mentioned that Harrington 1 

 records that out of 18 local epidemics of typhoid fever 

 investigated within *two years by the Massachusetts State 

 Board of Health 14 were milk-borne, only 3 being water- 

 borne, and 1 of unknown method of spread. 



The first outbreak traced to milk appears to have been at 

 Penrith in the autumn of 1857, and recorded by Taylor. In 

 this outbreak there were cases of typhoid fever in the cottage 

 of the milkman who supplied the infective milk. 



It is known that a good many cases of enteric fever are of 

 the ambulatory type, and continue about, and not infrequently 

 at work until a comparatively late stage of the disease, and after 

 they have been infectious for several weeks. We also know 

 that in recovered cases the bacilli may persist for very long 

 periods in the excretions of the patients, and that such persons, 

 although cured and apparently in perfect health, yet are 

 passing typhoid bacilli in their evacuations, and in consequence 

 are dangerous potential sources of infection. There are also a 

 not inconsiderable number of cases of quite unrecognised 

 typhoid fever, with symptoms so mild that the true nature 

 of the condition is not suspected, and these cases also may 

 act as carriers of infection. If these facts are associated 

 with the known carelessness of certain classes in regard to 

 personal cleanliness and the disposal of excreta, and the fact 

 that flies undoubtedly can infect milk with typhoid bacilli 

 from excreta, the frequency of milk-borne typhoid fever out- 

 breaks is readily understood. 



The actual ways in which milk may become infected with 

 typhoid bacilli are very numerous, but the methods of spread 

 illustrated below include all the chief channels of infection. 



1. Example of a Case of Typhoid Fever at the Farm not 

 properly isolated. At Clydach, Glamorgan, W. Williams 2 

 recorded an outbreak of 16 cases of enteric fever amongst 



1 New York Medical Journal, 1907, Ixxxv. p. 696. 

 2 Public Health, 1902, xiv. p. 650. 



