Risk factors for symptomatic and asymptomatic norovirus infection in the community

Abstract

SUMMARYThe 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 (1993England ( -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.

Enteric viruses in healthy children in cameroon: Viral load and genotyping of norovirus strains

“…NoV was detected in almost all subjects with multiple infections, regardless of age. This finding supports the evidence that NoV may be a major enteric virus in both children and adults [Phillips et al, 2010b].…”

Environmental Transmission of Human Noroviruses in Shellfish Waters

“…The 50% infectious dose (ID 50 ) was reported as 18 NoV genome copies for a disaggregated inoculum, whereas the probability of an infected subject becoming ill (i.e., expressing NoV symptoms) ranged from 10% at a dose of 10 3 NoV genomes to 70% at a dose of 10 8 virus genomes. This dose-dependent outcome may help explain why asymptomatic NoV excretion has been observed in a substantial proportion (up to 16%) of healthy individuals (121) and also, since reporting of outbreaks depends on expression of clinical symptoms, why NoV levels seen in shellfish associated with outbreaks are generally higher than background environmental levels (122). Assuming that NoV detected in shellfish is viable, then this dose-response model can give an indication of the likely outcome following consumption of the NoV levels observed in shellfish surveillance studies.…”

Norovirus diagnostics: options, applications and interpretations

“…In outbreak situations, it is likely that more than one of these routes of transmission contributes to the spread of no rovirus. Transmission may occur via a direct airborne route but this is so far unproven [25][26][27]. An infectious dose of <1000 particles has been reported, which is lo w when compared to the concentration of no rovirus shed in feces (10 4 -10 12 genomic copies/g) [28][29][30].…”