54 
Four cases gave a history of association with persons convalescing 
from typhoid fever. 
It seems fair to estimate the chances of these 65 cases having be- 
come infected by contact at about 50 per cent ; and so, adding 32 of 
these to the 70 considered as almost certainly having been infected 
by contact, there were 102, or about 19 per cent, of the 523 cases 
attributable to contact. These 102 cases compose about 15 per cent 
of the total 670 cases investigated, as compared with 6.23 per cent 
(estimated on the same basis of probability) of the 866 cases investi- 
gated in 1906. 
In endeavoring to determine what part, if any, chronic bacillus 
carriers have in the dissemination of typhoid fever infection in the 
District of Columbia, the following data in regard to association of 
the 523 cases with persons who had had typhoid fever within the five 
years previous were obtained : 
Association 30 days prior to onset Avith persons Avho 
had had typhoid fever Avithin— 
1 
Amount of association. 
Intimate. 
Fairly 
intimate. 
Slig-ht. 
1 
Total 
eases. 
Six months - _ 
2 
1 
1 
4 
One year _ _ _ __ 
8 
5 
3 ! 
16 
Tavo vears 
3 
5 
2 
10 
Three years _____ _ __ _ __ . 
5 
0 
1 - , 
14 
Pour years __ _ _ _____ 
! 2 
2 
0 
4 
Five years _ _ _ _ __ _ 
6 
3 
2 
11 
XoneVnoAvn 
1 
464 
Total - _ _ _ ___ _ _ __ _ _ 
28 
1 
i ' 
,A23 
For people living in large cities, exact data as to association during 
a period of thirty days with persons who have had, sometime within 
the previous five years, an attack of typhoid fever would be almost if 
not quite impossible to obtain, and so the data presented in the above 
table refer almost entirely to association with other members of the 
family or with intimate friends. The number of cases giving a 
history of such association is, therefore, necessarily far below the 
actual. « 
Effort was made to obtain from persons who had had typhoid 
within five years and with whom the cases had associated specimens 
of feces for bacteriological examination; but this effort did not meet 
Avith much success, as many of the people shoAved a reluctance, from 
perhaps some j^eculiar sense of delicacy, toward collection of the 
specimens. Some of the specimens were too old before they reached 
the laboratory to give reliable results. 
Data relatiA^e to newcomers in the residences at Avhich cases oc- 
curred are giA^en in the following table. By newcomers Ave mean 
