18 
TYPHOID PEVEK IN DISTRICT OF COLUMBIA. 
WATER. 
Of the 747 cases, 721, or 96.54 per cent, gave a definite history of 
having used unboiled Potomac water, supplied through the city 
system, as the sole, principal, or occasional source of water for drink- 
ing purposes during thirty days prior to onset of illness. 
Of the 26 cases occurring among persons who did not give a definite 
history of having drunk unboiled tap water, 2 were attributed to 
infection by contact, 7 to infection by milk, 1 to infection by ice 
cream, and 5 may have contracted their infection outside of the Dis- 
trict of Columbia. Seventeen drank unboiled milk supplied by the 
dealers of the District. 
The following table gives the source of water used for drinking 
purposes during the thirty days preceding the onset of illness, by the 
747 cases studied: 
Raw tap water : « 
Solely ■. 
Principally 
Occasionally 
Occasionally (?) 
Boiled tap water: 
Solely 
Principally 
Occasionally 
Filtered tap water: 
Solely 
Principally 
Occasionally 
Occasionally (?) 
Public pumps: 
Solely 
Principally 
Occasionally 
Occasionally (?) 
Bottled water: 
Solely 
Principally 
Occasionally 
Private wells or springs in District of Columbia: 
Solely 
Principally 
Occasionally 
Various sources out of District of Columbia: 
Principally 
Occasionally 
443 
196 
73 
12 
2 
47 
15 
T 
J. 
10 
3 
1 
1 
3 
94 
31 
1 
7 
13 
4 
36 
33 
0 
69 
By raw tap water is meant water as it comes from the taps and neither boiled nor 
filtered after it leaves the tap. The difference of 9 in the number of cases which used 
“raw’^ tap water and the number which used unboiled tap water is explained by the 
fact that all the tap water drunk by these 9 cases was filtered through some kind of a 
house filter. In none of these instances was the filtration considered efficient. 
