title: Case-control studies of sporadic enteric infections: a review and discussion of studies conducted internationally from 1990 to 2009.
abstract: Epidemiologists have used case-control studies to investigate enteric disease outbreaks for many decades. Increasingly, case-control studies are also used to investigate risk factors for sporadic (not outbreak-associated) disease. While the same basic approach is used, there are important differences between outbreak and sporadic disease settings that need to be considered in the design and implementation of the case-control study for sporadic disease. Through the International Collaboration on Enteric Disease "Burden of Illness" Studies (the International Collaboration), we reviewed 79 case-control studies of sporadic enteric infections caused by nine pathogens that were conducted in 22 countries and published from 1990 through to 2009. We highlight important methodological and study design issues (including case definition, control selection, and exposure assessment) and discuss how approaches to the study of sporadic enteric disease have changed over the last 20 years (e.g., making use of more sensitive case definitions, databases of controls, and computer-assisted interviewing). As our understanding of sporadic enteric infections grows, methods and topics for case-control studies are expected to continue to evolve; for example, advances in understanding of the role of immunity can be used to improve control selection, the apparent protective effects of certain foods can be further explored, and case-control studies can be used to provide population-based measures of the burden of disease.
authors.affiliation: Enteric Diseases Epidemiology Branch, Division of Foodborne, Waterborne, and Environmental Diseases, National Center for Emerging Zoonotic and Infectious Diseases, Centers for Disease Control and Prevention, Atlanta, Georgia, USA. kfullerton@cdc.gov
authors.forename: Kathleen E
authors.initials: KE
authors.lastname: Fullerton
authors.forename: Elaine
authors.initials: E
authors.lastname: Scallan
authors.forename: Martyn D
authors.initials: MD
authors.lastname: Kirk
authors.forename: Barbara E
authors.initials: BE
authors.lastname: Mahon
authors.forename: Frederick J
authors.initials: FJ
authors.lastname: Angulo
authors.forename: Henriette
authors.initials: H
authors.lastname: de Valk
authors.forename: Wilfrid
authors.initials: W
authors.lastname: van Pelt
authors.forename: Charmaine
authors.initials: C
authors.lastname: Gauci
authors.forename: Anja M
authors.initials: AM
authors.lastname: Hauri
authors.forename: Shannon
authors.initials: S
authors.lastname: Majowicz
authors.forename: Sarah J
authors.initials: SJ
authors.lastname: O'Brien
mesh_terms: D016022:Case-Control Studies; D004196:Disease Outbreaks; D014943:Global Health; D006801:Humans; D007410:Intestinal Diseases / Q000453:epidemiology* / Q000382:microbiology / Q000469:parasitology; D012107:Research Design; D012307:Risk Factors