21 
period. Therefore, it appears that the difference in rate for the two 
' summers may have been due to a difference in extent of operation of 
^.some factor or factors other than milk and contact. 
1 That the difference in prevalence of typhoid fever in Washington 
for the two summers was probably not due to a difference in tempera- 
ture or humidity is indicated by reports from Baltimore that t}q3hoid 
fever was fully as prevalent in that city in the summer of 1907 as in 
I that of 1906. The rise in both cities was belated in the summer of 
r 1907. 
So far as can be judged by reports received from various cities 
there has been no material difference in the prevalence of typhoid 
fever throughout the country during the two years. In some places 
there has been more, in others less, and in some about the same during 
the two years. 
, In the 1907 period there was relatively a considerably smaller 
I number of cases among the wealthy class of people than in the 1906 
period. Maps 1, 2, 3, 1, 5, 6, and 7 show the distribution of cases by 
(| place of residence when the disease was contracted. A comparison 
I of these maps with those showing the distribution of the cases studied 
: in 1906 (see Bulletin No. 35) shows a somewhat less uniform dis- 
ij tribution of cases during the half monthly periods of 1907. In 1907 
j| there was a quite general distribution of cases throughout the city, 
I I . but in proportion to population there was relatively a larger number 
I ^ of cases in the more unhygienic sections of the city. 
I i Therefore, it appears from our observations this year that typhoid 
I V fever may be quite uniformly and generally scattered throughout a 
I large city having water of good sanitary quality, so far as can be 
% . judged by our present bacteriological standards. It has been assumed 
that a more or less widespread and uniform distribution of an in- 
' fectious disease like typhoid fever points to a common factor, such 
as infected water. Whether this general distribution was due pri- 
marily to contaminated water in previous months or years, or to other 
causes, can only be determined by future studies. 
The Government Hospital for the Insane, with a population of 
' about 3,000 but with artesian well water, pasteurized milk and gen- 
; erally good sanitary conditions, again this season remained free of 
infection. One case occurred among the employees of the institution, 
i . but this case was a man who made frequent visits to, and took meals 
I at his home in, Washington. 
The total number of cases of typhoid fever in the District of Co- 
lumbia reported to the health office during the calendar year 1907 
was 945 as against 1,126 for the calendar year 1906. Thus, the ty- 
phoid fever morbidity rate in the District of Columbia for the calen- 
dar year 1907 was 2.87 per 1,000 of population, or one person in 
:!; _ ■ . 
'k- > • . 
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