Comparative assessment of primary and secondary infection risks in a norovirus outbreak using a household model simulation
Fuminari Miura
,
Toru Watanabe
,
Kozo Watanabe
,
Kazuhiko Takemoto
,
Kensuke Fukushi
DOI:10.1016/j.jes.2016.05.041
Received January 31, 2016,Revised April 09, 2016, Accepted May 09, 2016, Available online September 15, 2016
Volume 28,2016,Pages 13-20
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.
