title: Risk factors for symptomatic and asymptomatic norovirus infection in the community.
abstract: The objective of this study was to investigate risk factors for norovirus-associated infectious intestinal disease (IID) and asymptomatic norovirus infection. Individuals with IID and healthy controls were recruited in a community-based study in England (1993-1996). This is the first risk-factor study to use viral load measurements, generated by real-time RT-PCR, to identify cases of norovirus-associated IID and asymptomatic infections. Using multivariable logistic regression the main risk factor identified for norovirus-associated IID was contact with a person with IID symptoms. Infectious contacts accounted for 54% of norovirus cases in young children and 39% of norovirus cases in older children and adults. For young children, contacts outside the household presented the highest risk; for older children and adults, the highest risk was associated with child contacts inside the household. Foreign travel and consumption of shellfish increased the risk of norovirus-associated IID. Lifestyle and dietary factors were associated with a decreased risk of both norovirus-associated IID and asymptomatic infection. No risk factors were identified for asymptomatic norovirus infection.
authors.affiliation: Department of Epidemiology and Population Health, London School of Hygiene and Tropical Medicine, London, UK. g.phillips@uel.ac.uk
authors.forename: G
authors.initials: G
authors.lastname: Phillips
authors.forename: C C
authors.initials: CC
authors.lastname: Tam
authors.forename: L C
authors.initials: LC
authors.lastname: Rodrigues
authors.forename: B
authors.initials: B
authors.lastname: Lopman
mesh_terms: D000293:Adolescent; D000328:Adult; D058345:Asymptomatic Infections / Q000453:epidemiology*; D017250:Caliciviridae Infections / Q000453:epidemiology* / Q000821:virology; D016022:Case-Control Studies; D002648:Child; D002675:Child, Preschool; D017714:Community-Acquired Infections / Q000453:epidemiology* / Q000821:virology; D004739:England / Q000453:epidemiology; D005191:Family Characteristics; D005247:Feeding Behavior; D005759:Gastroenteritis / Q000453:epidemiology* / Q000821:virology; D006801:Humans; D007223:Infant; D015999:Multivariate Analysis; D029322:Norovirus / Q000302:isolation & purification*; D012307:Risk Factors; D014195:Travel