32 
TYPHOID FEVER IN DISTRICT OF COLUMBIA. 
Colon bacilli are found in tbe water. These organisms are usually 
taken as an indication of sewage pollution. Sixty-six and six tenths 
per cent of the 1 5 samples of the river water examined contained the 
colon bacillus; 14.3 per cent of the 21 samples of filtered water, and 
17.5 per cent of the 131 samples of tap water examined contained 
the colon bacillus in 1 and 10 cc. 
It is evident, therefore, that a certain number of the colon bacilli 
in the raw water pass the storage reservoirs and sand filters. There- 
fore it seems reasonable to assume that a certain number of typhoid 
bacilli, when present in the raw water, may also pass into the tap 
water. 
The Potomac River at numerous points along its course receives 
the sewage of a number of thousands of persons. 
Some of the typhoid fever in the District in former j^ears was 
apparently traced to the Potomac River water. For example, the 
outbreak in Cumberland, Md. (December, 1889, to April, 1890), was 
followed by an increase in typhoid fever in the early spring in Wash- 
ington. A sudden decrease in the Washington death rate followed 
the installation of the Dalecarlia reservoir in 1895. (See p. 224.) 
The tvnhoid death rate for 1906 — that is, since the filtration of the 
water — was 49.3 per 100,000. This is a much higher typhoid death 
rate than is usually observed for large American and European cities 
having water supplies of undoubted purity. 
Considering that there were due to contact and to infected milk 
twice as many cases as we were able to attribute fairly definitely to 
these causes, there still remains about half of the cases unaccounted 
for. If the water is not a factor in the spread of the infection, then 
it would appear that some unknown agent or agents for the dissem- 
ination of the infection must be peculiarly active in Washington. 
In favor of the view that the Potomac water 'plays little, if any, role in 
the dissemination of typhoid fever in Washington, we hdve the following: 
The improvement in the water supply was not followed by an 
improvement in the typhoid fever situation. 
Typhoid fever may diffuse itself broadcast throughout a com- 
munity using water free from suspicion — the so-called ^‘prosodemic’’ 
type of Sedgwick and Winslow.® 
The great majority of the population of Washington drink unboiled 
tap water, which may be considered as diminishing the value of the 
suggestion that the tap water is a common factor. 
The colon bacdlus is not the typhoid bacillus, and the sanitary 
significance of the presence of colon bacilli in amounts less than Icc. 
® Sedgwick^ W. T., and Winslow, C. E. A. Statistical Studies on the Seasonal 
Prevalence of Typhoid Fever, etc. Memoirs of the Amer. Acad, of Arts and Sciences, 
xii, p. 568. 1902. 
