Person-to-person spread of Salmonella typhimurium phage type 10 after a common-source outbreak

An outbreak of gastroenteritis caused by Salmonella typhimurium phage type 10 in a university hall of residence affected 66 students and one member of staff. Results of a questionnaire survey of students suggested that the main wave of (53) cases was due to consumption of contaminated cottage pie, but the remaining cases could best be explained by person-to-person spread of infection. Investigation of the outbreak was greatly assisted by rigorous case finding, the screening of those at risk for symptomless excretors, and the collection of food histories from those who remained well. The possibility of person-to-person spread of salmonella food-poisoning serotypes should be borne in mind when outbreaks are investigated in closed communities such as institutions, families, and ships.