a1 Department of Epidemiology, School of Public Health, University of North Carolina, Chapel Hill, NC, USA
a2 Division of Foodborne, Bacterial and Mycotic Diseases, National Center for Zoonoses, Vectorborne and Enteric Diseases, Centers for Disease Control and Prevention, Atlanta, GA, USA
a3 Department of Environmental Health, University of Minnesota School of Public Health, Minneapolis, MN, USA
a4 Division of Infectious Diseases, School of Medicine, University of North Carolina, Chapel Hill, NC, USA
Use of well persons as the comparison group for laboratory-confirmed cases of sporadic salmonellosis may introduce ascertainment bias into case-control studies. Data from the 1996–1997 FoodNet case-control study of laboratory-confirmed Salmonella serogroups B and D infection were used to estimate the effect of specific behaviours and foods on infection with Salmonella serotype Enteritidis (SE). Persons with laboratory-confirmed Salmonella of other serotypes acted as the comparison group. The analysis included 173 SE cases and 268 non-SE controls. SE was associated with international travel, consumption of chicken prepared outside the home, and consumption of undercooked eggs prepared outside the home in the 5 days prior to diarrhoea onset. SE phage type 4 was associated with international travel and consumption of undercooked eggs prepared outside the home. The use of ill controls can be a useful tool in identifying risk factors for sporadic cases of Salmonella.
(Accepted May 21 2008)
(Online publication July 09 2008)