Biology Reference
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substantially, and salad bars had been implicated as a major source of in-
fection. On that day, state health officials ordered all salad bars in the city
closed and requested assistance from the CDC. The epidemic ended with
the last case on 10 October.
The outbreak was caused by a strain of
Salmonella enteritica
serotype
typhimurium that has rarely been implicated in outbreaks. However, it
caused two (and possibly three) other outbreaks in Oregon in late 1984,
so its occurrence in The Dalles was relatively unremarkable.
The outbreak occurred in two waves (figure 14.1). Thirteen percent of
the cases were in the first wave, from 9 to 18 September (peaking on 15
September), and were linked to only 2 restaurants. The second wave,
from 22 September to 10 October (peaking on 24 September), produced
87 percent of the cases and was associated with 10 to 22 restaurants (in-
200
180
160
140
120
100
80
60
40
20
0
91113 15
17
19
21 23
25 27 29
1
3
5
79
September
October
Date of Onset
Figure 14.1
The salmonellosis outbreak in The Dalles, Oregon, in late 1984.
(Source: CDC, “Restaurant-Associated
Salmonella typhimurium
Gastroenteritis, The Dalles, Oregon, 1984,” limited-distribution report, EPI-
84-93-2, 1 November 1988.)
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