TYPHOID FEVEPt IN DISTRICT OF COLUMBIA. 
51 
thirty days prior to onset of illness outside of the District of Columbia 
and may have contracted their infection while away. Seventeen 
used unboiled milk supplied by the dealers of the District of Columbia. 
The following table gives the source of water used for drinking 
purposes during the thirty days preceding onset of illness by the 747 
cases studied: 
Water used by cases thirty days prior to illness. 
Raw tap water 
Solely 443 
Principally 196 
Occasionally 73 
Occasionally (?) 12 
Boiled tap water: 
Solely 2 
Principally 47 
Occasionally 15 
Filtered tap water: 
Solely 1 
Principally 10 
Occasionally 3 
Occasionally (?) 1 
Public pumps: 
Solely 1 
Principally 3 
Occasionally 94 
Occasionally (?) 31 
Bottled water: 
Solely 1 
Principally 7 
Occasionally 13 
Private wells or springs in the District of Columbia: 
Solely 4 
Principally 36 
Occasionally 33 
Various sources out of the District of Columbia: 
Principally 0 
Occasionally 69 
Melted ice: 
Solely 1 
Principally 1 
These figures point to the water as a factor in the spread of the 
infection, but we must remember that perhaps an equally large pro- 
portion of the general population drink the raw tap water. For a 
full discussion of the relation of the Potomac Kiver water to typhoid 
fever see page 30, et seq. 
O' By raw tap water is meant that the water was not boiled or filtered after it left the tap. 
