Understanding foodborne transmission mechanisms for Norovirus: A study for the UK's Food Standards Agency

The paper outlines the 'complete arc' of a range of modelling activities initiated by UK's Food Standards Agency (FSA). Norovirus produces infectious intestinal disease in humans via both person-to-person contact (P2P) and foodborne (FB) transmission. The FSA commissioned a research study to improve understanding of FB mechanisms, and of where it might target its efforts. In response, an existing P2P model with a single, exogenous parameter for FB transmission was transformed into a System Dynamics model of FB processes. The modelling involved individual interviews and a facilitated group modelling session, the FSA providing access to relevant experts. Contamination routes modelled concerned: bi-valve shellfish; sludge; some fruits and vegetables; other foodstuffs. This large model showed it was possible to give an account of the underlying causal mechanisms; and it facilitated a categorisation of parameters in a manner useful in agenda-setting for future research and in identifying policy levers. Some creative thinking extended the work in an unexpected but significant way. Data and mathematical analysis made it possible to calibrate a P2P model for the first time. Sensitivity analysis then suggested that small changes in human behaviour could explain the tenfold seasonal variation in Norovirus cases, and also offered an understanding of the relative importance of FB and P2P vectors. The range of consequences of the study included an increased understanding by the FSA of the different means of trying to control Norovirus, practical actions and ideas for further work. (C) 2018 The Authors. Published by Elsevier B.V.