Descriptive epidemiological evidence refers to generation of hypotheses concerning the food vehicle of an outbreak by systematic collection of information on outbreak cases, description of the outbreak with regard to time, place and person, and examination of the characteristics (e.g. age, sex, race/ethnicity, residence, occupation, recent travel or attendance at events) of those who are ill. It includes the systematic evaluation of cases’ food histories, as the identification of common food exposures, by using consistent and standardised means (such as standard trawling questionnaires) to obtain information from all, or an appropriate subset of, outbreak cases about food consumed in the period when infection is likely to have occurred