Introduction: Three cases of laboratory confirmed Salmonella paratyphi B and an unexpected high number of deaths at a nursing home were reported by the local health authority of Gothenburg to the Swedish Institute for Infectious Diseases Control (SMI) on 2 April 1998. An epidemiological investigation started on 4 April in order to determine the extend of the outbreak, identify its source and to propose control measures. The objectives of the study were: 1. Investigation of links between increased mortality and an outbreak of S. paratyphi B. 2. Identification of risk factors for contracting an paratyphoid fever – like disease or death.