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Table 1 Summary of model assumptions trialled for norovirus, where each model was fitted to age-specific incidence data in England. Models A0–B20 were taken forward to estimate incidence of norovirus between 2020 and 2022

From: Predicted norovirus resurgence in 2021–2022 due to the relaxation of nonpharmaceutical interventions associated with COVID-19 restrictions in England: a mathematical modeling study

Model A0 A20 B0 B20 D0 D20 E0 F0
Assumptions
 First infection Always symptomatic Always symptomatic Always symptomatic Always symptomatic 50% asymptomatic 50% asymptomatic 50% asymptomatic Always symptomatic
 Duration of Asymptomatic infectiousness (days) 15 15 20 20 15 15 15 15
 Asymptomatic infectiousness relative to symptomatic 0.05 0.05 0.05 0.05 0.05 0.05 0.5 1
 Under-reporting assumed in fitted data (%) 0 20 0 20 0 20 0 0
Results
 Probability of transmission given a contact (qs) 0.1892696 0.2070616 0.1693301 0.1824529 0.2183579 0.2193598 0.374627 0.1909186
 Log-likelihood of age-specific incidence when fitted to data from England [15] −77.94 −190.03 −72.10 −107.46 −667.77 −850.36 −1458.08 −1454.57
 R0 (at endemic equilibrium) 1.81 2.03 1.81 2.01 1.94 1.62 >10 >10
 Shedding prevalence (at endemic equilibrium) (%) 0.18 0.25 0.303 0.41 0.718 0.70 59.44 59.77
 Sero-prevalence (at endemic equilibrium) (%) 24.64 30.55 24.54 29.92 27.73 37.80 20.49 20.17
 Comments Good fit; used for 2020–2022 projections Good fit; used for 2020–2022 projections Good fit; used for 2020–2022 projections Good fit; used for 2020–2022 projections Poor fit to data, incidence in younger ages was under-estimated and incidence in older ages was over-estimated Poor fit to data, incidence in younger ages was under-estimated and incidence in older ages was over-estimated Poor fit to the incidence data (high incidence in adults) and unrealistic R0, but better comparison with expected seroprevalence and shedding Poor fit to the incidence data (high incidence in adults) and unrealistic R0, but better comparison with expected seroprevalence and shedding