ACUTE INFECTIOUS DISEASES 77 



for a large epidemic appears to be that at Enfield in 1887 

 recorded by Bruce -Low, in which there were forty -eight 

 deaths with a case- mortality of 22'5 per cent. Excluding all 

 outbreaks in which the deaths are not clearly set out, the case- 

 mortality in the epidemics recorded by Trask, taking them 

 all together, was 16*1 per cent. From these figures it would 

 appear that the case-mortality does not materially differ from 

 that of epidemics spread by means other than milk. 



In a number of the outbreaks it has not been possible to 

 find the source of infection of the milk. In the few rare cases 

 recorded in Chapter VI. the cow has been implicated. In the 

 majority of cases in which the source has been ascertained it 

 has been traced to a person handling the milk who has either 

 had a slight attack of diphtheria, is in charge of or brought 

 into close contact with a sufferer from diphtheria, or who is 

 a diphtheria carrier. The outbreaks in which a diphtheria 

 carrier is the source of the infection are sometimes difficult to 

 prove, and probably a number of the earlier recorded epi- 

 demics in which the cause could not be traced, and for which 

 bacteriological facilities were not available, were due to infection 

 of the milk from either slight and unrecognised cases, or from 

 true carriers. 



Apparently no outbreaks have been traced from infected 

 water or other indirect . sources. 



The following little outbreak illustrates the importance 

 of bacteriology in tracing milk epidemics. It is recorded 

 by Chase. 1 Two children in a milkman's house developed 

 diphtheria, and were removed to hospital and isolated there. 

 All the members of the household were examined bacteriologic- 

 ally, but no diphtheria bacilli were found. Three weeks later 

 cases of diphtheria began to appear among the customers in 

 Brookline (Massachusetts). In Brookline only seven or eight 

 families used his milk, and cases of diphtheria developed in 

 four of these. Cases were also found in Boston receiving -his- 

 milk. On re-examination of the inmates of the milkman's 

 house and others handling the milk virulent diphtheria bacilli 

 were found in the throats of three men. Up to this time two 

 of them had been employed in milking the cows. 



The following is a good example of a milk-spread diphtheria 



1 Journ. Mass. Assoc. Board of Health, 1900, p. 5. 



