From:  http://www.cdc.gov/epo/mmwr/preview/mmwrhtml/mm4910a3.htm

"Of 343 company employees who ate luncheon food, 191 (56%) had an illness
meeting the case definition. Among ill luncheon attendees, symptoms included
nausea (87%), diarrhea (80%), abdominal pain (75%), chills (73%), vomiting
(70%), and headache (65%). Illness onsets occurred a median of 33 hours after
eating the lunch (range: 6--96 hours) (Figure 1), and the median duration of
illness was 24 hours (range: 5--120 hours). Of 236 luncheon attendees who ate
potato salad, 183 (78%) became ill. In addition, eight (89%) of nine
restaurant patrons who responded ate potato salad and became ill. Among
luncheon attendees, eating potato salad was associated strongly with illness
(odds ratio=42.7; 95% confidence interval=18.6--101.7). The potato salad was
prepared 2 days before the luncheon by two foodhandlers, one of whom was ill.
The ill foodhandler used bare hands to mix the ingredients in a 12-gallon
plastic container."