*Values are no. (%) except as indicated. CCI, Charlson comorbidity index; CDI, Clostridioides difficile infection; COPD, chronic obstructive pulmonary disease; CRP, C-reactive protein; CVA, cerebrovascular accident; HSCT, hematopoietic stem cell transplantation; IBD, inflammatory bowel disease; IQR, interquartile range; NA, not applicable. †A univariate logistic regression was used to compute p values, comparing secondary transmission with nonsecondary transmission. ‡A generalized linear mixed model was used to compute p values after adjusting for variables exhibiting statistical significance in the univariate analysis; the model was used to elucidate the odds of subsequent CDI occurrence. The odds ratios and 95% CIs for each variable are shown in Appendix 1 Table 2. §Because 744 patients experienced >2 episodes of contact with separate index patients, a disparity emerged between the number of contact cases and the number of contact patients. ¶Group 1 included patients who had direct contact with index patients. #Co-hospitalization in the same bedroom with the index patient for >24 hours. **Contact with index patient who had diarrhea. ††Group 2 included patients who had indirect contact with index patients via healthcare personnel. ‡‡Group 3 included patients who had indirect contact with index patients via the environment.