accounting for a total of 306 people, most of
whom had eaten from the buffet (see Table 1).
Seventy-seven confirmed and probable cases
among these 306 individuals gives an attack rate
for salmonellosis of 25.2%. However, this calculation
was based on groups of people in which
one person is bound to have been ill. Excluding
one patient from each group, there were 18
patients among a total of 247 individuals, which
gives an attack rate of 7.3%. Finally, a third
estimate was based on the total number of known
patients relative to all exposed persons, i.e., all
customers of the restaurant. The total of 77 known
cases, in conjunction with a total of 5357 paying
customers between 17 July and 4 August (as
indicated by the restaurant accounts), gives a
minimal attack rate of 1.4%.