Risk factors for symptomatic and asymptomatic norovirus infection in the community

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.

Citation:
Phillips, G., Tam, C.C., Rodrigues, L.C. and Lopman, B. (2010), 'Risk factors for symptomatic and asymptomatic norovirus infection in the community', Epidemiology & Infection, 139(11), pp. 1676-1686, doi:10.1017/S0950268810002839.