title: Shedding of norovirus in symptomatic and asymptomatic infections.
abstract: 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.
authors.affiliation: CIb/RIVM,Epidemiology and Surveillance Unit,Bilthoven,The Netherlands.
authors.forename: P F M
authors.initials: PF
authors.lastname: Teunis
authors.affiliation: CIb/RIVM,Laboratory for Infectious Diseases and Perinatal Screening,Bilthoven,The Netherlands.
authors.forename: F H A
authors.initials: FH
authors.lastname: Sukhrie
authors.affiliation: CIb/RIVM,Laboratory for Infectious Diseases and Perinatal Screening,Bilthoven,The Netherlands.
authors.forename: H
authors.initials: H
authors.lastname: Vennema
authors.affiliation: Erasmus Medical Centre,Department of Virology,Rotterdam,The Netherlands.
authors.forename: J
authors.initials: J
authors.lastname: Bogerman
authors.affiliation: Erasmus Medical Centre,Department of Virology,Rotterdam,The Netherlands.
authors.forename: M F C
authors.initials: MF
authors.lastname: Beersma
authors.affiliation: Erasmus Medical Centre,Department of Virology,Rotterdam,The Netherlands.
authors.forename: M P G
authors.initials: MP
authors.lastname: Koopmans
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D058345:Asymptomatic Infections; D001499:Bayes Theorem; D017250:Caliciviridae Infections / Q000453:epidemiology / Q000635:transmission / Q000821:virology*; D015331:Cohort Studies; D004196:Disease Outbreaks; D005243:Feces / Q000821:virology*; D005260:Female; D005759:Gastroenteritis / Q000453:epidemiology / Q000821:virology*; D006282:Health Personnel / Q000706:statistics & numerical data; D006761:Hospitals; D006801:Humans; D017758:Infectious Disease Transmission, Patient-to-Professional; D017757:Infectious Disease Transmission, Professional-to-Patient; D008137:Longitudinal Studies; D008297:Male; D008875:Middle Aged; D055361:Multilevel Analysis; D029322:Norovirus / Q000235:genetics*; D009735:Nursing Homes; D012367:RNA, Viral / Q000032:analysis*; D060888:Real-Time Polymerase Chain Reaction; D017201:Virus Shedding / Q000502:physiology*; D055815:Young Adult
chemical_list: D012367:RNA, Viral
keywords: virus infection