The Supply and Uses of Water 207 



means of transmission. We shall study the water supply in 

 relation to this question. Let us consider typhoid fever as 

 epidemic (meaning " among the people")? in which case the 

 disease may be traced to a common source or means of trans- 

 mission, such as the milk or water supply of a community. 

 Typhoid fever may be widely scattered, that is, individual 

 cases may be found in many different localities ; but our con- 

 cern is with the epidemic and not such individual cases. A 

 typical instance of many epidemics which helped to establish 

 the connection of disease with the water supply may be given 

 in some detail. 



In January and February, 1912, a city of 50,000 population 

 in the northern part of Illinois had 10,000 cases of enteritis, 

 similar to typhoid, and 199 cases of typhoid fever. As the 

 epidemic occurred in midwinter, it could not have been dis- 

 tributed by the house-fly. It soon appeared that the only 

 probable agencies were the milk and water supply. 



The milk supply was quickly shown to be free from contamina- 

 tion. Fifty different dealers supplied the families in which 

 the disease had developed, and in no instance was there a dis- 

 proportionate number of cases on any one milk route. There- 

 fore the milk supply was not the medium through which the 

 germs were transmitted. 



The water supply was investigated. Many families who had 

 private wells escaped infection. Another interesting fact was 

 discovered. A group of factories provided their employees with 

 drinking water from private wells. Only six per cent of these 

 employees developed cases of enteritis. Another group of 

 factories provided their employees with water from the city 

 mains. Seventy per cent of this group developed the disease. 



The location of the source of the trouble was made possible 

 by another occurrence. A destructive fire about the middle 

 of January, just before the epidemic, had largely depleted the 

 storage reservoir. To fill this, a well which had not been in 

 use for a long time, was pumped. Test showed that the water 



