In this study, the guests and waiters were identified as the study objects, and the investigation focused on the infection patterns of the guests. After the outbreak, 83 of 126 guests from six parties were interviewed, 52 of whom reported illness. As shown in Figure 1, the distribution of attack rates showed a statistically significant spatial pattern . The attack rate was highest at Table 2, where the index patient was seated, while the rates at other tables decreased as the distance from Table 2 increased.