The nature of this outbreak highlights several changing features of foodborne disease epidemiology, including the enhanced mobility of persons through air travel, an increasing reliance on pre-processed foods, and an expanding immunocompromised population at risk. Through a Web-based investigation, we were able to rapidly identify the source of this outbreak and inform an immunocompromised population of its potential risk for illness. Our approach allowed us to contact and question several hundred geographically dispersed persons in a matter of days. Survey respondents' answers were automatically stored in a secure electronic database, eliminating the need for data entry. With the development of questionnaire templates, a public health official could select sets of questions and precoded answers from pull-down menus and modify them to design an outbreak-specific, Web-based questionnaire that is automatically linked to an electronic database (5) . These methods make it increasingly possible to design and post a Web-based investigative tool for wide distribution within hours.