title: Comparative assessment of primary and secondary infection risks in a norovirus outbreak using a household model simulation.
abstract: Diarrheal diseases can be transmitted via both primary infection due to exposures to contaminated materials from the environment and secondary infection due to person-to-person contacts. Usually, the importance of secondary infection is empirically assessed by fitting mathematical models to the epidemic curves. However, these empirical models may not be applicable to other epidemic cases because they are developed only for the target epidemics and they don't consider the detail routes of infection. In our previous study, we developed a theoretical model taking into account the various routes of infection that commonly occur in households (e.g., shaking hands, food handling, and changing diapers). This model was made flexible and applicable to any epidemics by means of adjusting model parameters. In this study, we proposed a new index "Vulnerability indicator to secondary infection (VISI)", which expressed a ratio of secondary infection to primary infection risks and calculated this index in a simulated norovirus (NoV) epidemic that involved 10,000 households. The results demonstrated that households composed of more than three members including infant(s) had much higher levels of VISI (5-45) than two-member-households with VISI (0.1-4). These results concluded that the infants were likely to be a hub of secondary infections in highly dense families and therefore careful handling of diapers was deemed indispensible in such families to effectively control the secondary infections.
authors.affiliation: Department of Urban Engineering, Graduate School of Engineering, the University of Tokyo, Tokyo 113-8654, Japan. Electronic address: mirua@env.t.u-tokyo.ac.jp.
authors.forename: Fuminari
authors.initials: F
authors.lastname: Miura
authors.affiliation: Department of Food, Life and Environmental Sciences, Faculty of Agriculture, Yamagata University, Yamagata 997-8555, Japan.
authors.forename: Toru
authors.initials: T
authors.lastname: Watanabe
authors.affiliation: Department of Civil and Environmental Engineering, Ehime University, Ehime 790-8577, Japan.
authors.forename: Kozo
authors.initials: K
authors.lastname: Watanabe
authors.affiliation: Institute for the Advanced Study of Sustainability, the United Nations University, Tokyo 150-8925, Japan.
authors.forename: Kazuhiko
authors.initials: K
authors.lastname: Takemoto
authors.affiliation: Todai Institutes for Advanced Study (TODIAS), Integrated Research System for Sustainability Science (IR3S), The University of Tokyo, Tokyo 113-8654, Japan.
authors.forename: Kensuke
authors.initials: K
authors.lastname: Fukushi
mesh_terms: D017250:Caliciviridae Infections / Q000453:epidemiology*; D060085:Coinfection / Q000453:epidemiology*; D004196:Disease Outbreaks / Q000706:statistics & numerical data; D005191:Family Characteristics; D005759:Gastroenteritis / Q000453:epidemiology*; D006801:Humans; D008962:Models, Theoretical; D029322:Norovirus; D018570:Risk Assessment
keywords: Norovirus; Quantitative microbial risk assessment; Secondary infection