Methodology minute: An overview of the case-case study design and its applications in infection prevention.

The case-case study design is a potentially useful tool for infection preventionists during outbreak or cluster investigations. This column clarifies terminology related to case-case, case-control, and case-case-control study designs. Examples of practical applications of the case-case study design include determining risk factors for health care-onset versus community-onset infections, or antibiotic-resistant versus antibiotic-susceptible infections.