Shedding of norovirus in symptomatic and asymptomatic infections

• Published in: Epidemiology and infection Vol. 143; no. 8; pp. 1710 - 1717
• Main Authors: TEUNIS, P. F. M., SUKHRIE, F. H. A., VENNEMA, H., BOGERMAN, J., BEERSMA, M. F. C., KOOPMANS, M. P. G.
• Format: Journal Article
• Language: English
• Published: Cambridge, UK Cambridge University Press 01.06.2015
• Subjects: Adolescent; Adult; Aged; Aged, 80 and over; Asymptomatic; Asymptomatic Infections; Bayes Theorem; Caliciviridae Infections - epidemiology; Caliciviridae Infections - transmission; Caliciviridae Infections - virology; Cohort Studies; Consent; Disease Outbreaks; Epidemics; Feces - virology; Female; Gastroenteritis; Gastroenteritis - epidemiology; Gastroenteritis - virology; Gastrointestinal infections; Health Personnel - statistics & numerical data; Hospitals; Humans; Infections; Infectious Disease Transmission, Patient-to-Professional; Infectious Disease Transmission, Professional-to-Patient; Longitudinal Studies; Male; Medical personnel; Middle Aged; Multilevel Analysis; Norovirus; Norovirus - genetics; Nursing Homes; Original Papers; Patients; Real-Time Polymerase Chain Reaction; RNA, Viral - analysis; Transfer RNA; Virus Shedding - physiology; Viruses; Young Adult; gastrointestinal infections; Asymptomatic viral infections; Norwalk agent and related viruses; virology (human) and epidemiology; virus infection
• DOI: 10.1017/S095026881400274X
• ISSN: 0950-2688; 1469-4409

Norovirus is the most frequent cause of acute infectious gastroenteritis and it is difficult to control in crowded environments like hospitals and nursing homes. Transmission depends on oral intake of virus deposited in the environment by infectious subjects. Data from volunteer studies indicate that virus concentrations in stool are highly variable, but systematic studies of the time-course of shedding and its individual variation are lacking. This paper quantifies norovirus shedding in a large population of 102 subjects, including asymptomatic shedders, and uses a longitudinal model to generalize shedding patterns. Enhanced surveillance for studies of transmission of norovirus in hospital outbreaks has yielded a considerable number of faecal samples from symptomatic and asymptomatic shedders, both from patients and staff. Norovirus concentrations were determined by real-time PCR. A quantitative dynamic model was fitted to the shedding data, in a multilevel Bayesian framework, to study the time-course of shedding and its variation. The results indicate that shedding in asymptomatic subjects is similar to that in symptomatic infections, both showing considerable variation in peak levels (average 105−109 /g faeces) as well as duration of virus shedding (average 8–60 days). Patients appear to shed higher numbers of virus than staff, for slightly longer durations, but the differences are too small to be significant. Given equal shedding, the greater contribution of symptomatic cases to transmission must be caused by their higher efficiency in spreading these viruses. The results of this study will be helpful for risk studies that need to quantify the deposition of virus in the environment.