53 
The following table gives the interval in days elapsing between 
the definite onset of illness of the TO secondaiw cases and the definite 
onset of the primary cases from which these 70 cases were considered 
to have contracted the infection : 
Xumber of days elapsing- 
betAveen onset of primary 
and secondary case. 
Xumber 
of sec- 
ondary 
cases.— 
Xumber of days elapsing 
betAveen onset of primary 
and secondary case. 
1 
Xumber 
of sec- 
ondary 
1 cases. 
• 
2 
35 
1 
8 
3 
36 
1 
9 
4 
39 
1 
10 
3 
40 
• 1 
11 
3 
41 
1 
12 
2 
44 
1 
14 
1 
46 
1 
16 
1 
48 
1 
17 
1 
51 
1 
18 
2 
53 
1 
19 
2 
54 
1 
20 
1 
Xot accurately determined- 
6 
21 
1 
InterA’al not determined, 
22 
1 
secondary cases being 
24 
2 
among physicians, nurses. 
2.1 
3 
helpers, or inmates of 
27 
1 
hospitals AA*ho Avere more 
28 
2 
or less constantly ex- 
29 
2 
posed 
12 
30 
2 
Total - 
70 
31 
1 
1 
1 
33 
1 
I 
.i 
These figures emphasize the importance of exercising the utmost 
precautions to prevent the spread of infection from typhoid fever 
patients from the onset to the end of the illness. 
Among the cases not definitely attributable to a known factor there 
were 16 which gave a history of association with febrile cases sus- 
pected to be but not reported as typhoid fever. In 15 cases indirect 
conveyance of infection by persons or flies was strongly suggested. 
In determining that conveyance of infection by flies was probable 
the proximity of the house occupied by the primary case to that oc- 
cupied by the .secondary *case. the number of flies « in the neighbor- 
hood and the ease with which they could pass from the infected ex- 
creta of the primary case to the food of the secondary case, and all 
other conditions thought to have any bearing on the situation, were 
taken into consideration. 
“ It is difficult to estimate the part played by flies in spreading the infection of 
typhoid in a city having a good sewerage system. However, it is evidently 
advisable to lessen their number, which may be successfully done in a com- 
munity by the proper disposal of manure. 
