Swimmer recall on a Recreational Waterborne Illness outbreak questionnaire

Swimming pool outbreak investigators often rely on swimmers to recall pool-use activities and behaviors by questionnaire, as Recreational Waterborne Illness (RWI) does not occur immediately after exposure. Recall bias is common when questionnaires are used in retrospective data collection, and can alter the validity of associations found during statistical analysis. The purpose of this study was to assess swimmer activity recall on a self-administered questionnaire developed for RWI outbreak investigators in order to identify questions that need improvement. Questions associated with recall bias were identified by issuing the questionnaire once immediately and once one week after study participants swam in pool water. Participants experienced the most difficulty recalling reported water ingestion volumes (28% difference), skill level (25% difference), swimming in the deep end (23% difference), getting water up the nose (22% difference), and diving (22% difference). Activities and behaviors statistically associated with RWI incidence are often used to identify risk factors of disease, and where research and mitigation strategies should focus. Results from this research suggest pool outbreak investigators should consider and/or disclose response recall uncertainties when reporting statistical associations between RWI and swimmer activities, and that questions with high response rate differences should be adjusted in future exposure assessments.