Table 2.
Model Parameter Estimates and Bayesian Information Criteria for Best-Fit Models for Each Scenario
| Parameter Definition | Symbol | Prior Distribution | Scenario 1 | Scenario 2 | Scenario 3 | Scenario 4 |
|---|---|---|---|---|---|---|
| Basic reproductive number for short-cycle transmission | R0,p | Uniform (0,10) | 0.61 | 1.6 | 0.04 | 1.6 |
| Basic reproductive number for long-cycle transmission | R0,w | Uniform (0,10) | 0.71, 2.2a | 4.7 | 5.5 | 2.1 |
| Amplitude of seasonal forcing (long-cycle transmission) | q | Uniform (0,1) | 0.41 | 0.37 | 0.26 | 0.53 |
| Rate of waning immunity to clinical disease (years−1) | ϵ | Uniform (0,2) | 3.4 × 10−6 | 1.5 | 3.6 × 10−7 | 1.0 × 10−6 |
| Relative infectiousness of chronic and short-term carriers | r | Uniform (0,1) | 0.047 | 0.068 | 0.43 | 0.26 |
| Reporting fraction | f | Uniform (0,1) | 0.0087 | 0.0053 | 0.0029 | 0.0027 |
| Proportionality factor between incidence of Salmonella Enteritidis infection and observed incidence of invasive disease | mX | Uniform (1,Nb) | … | 1500 | … | … |
| Duration of cross-immunity, wk | 1/χ | Uniform (1, 1000) | … | 993 | … | … |
| Beginning week of increase in the duration of infectiousness or transmission rate | t0 | Uniform (0,Lc) | … | … | 27 February 2011 | 21 November 2010 |
| End week of increase in duration of infectiousness or transmission rate | t1 | Uniform (0,Lc) | … | … | 13 March 2013 | 10 March 2013 |
| Magnitude of increase in duration of infectiousness or transmission rate | m | Uniform (1,10) | … | … | 2.3 | 3.0 |
| Bayesian information criteria | 6626 | 6242 | 5941 | 5985 |
a R0,w varied with population size in scenario 1; the values listed correspond to the range of R0,w between January 1996 and February 2015.
b N represents the total population size in 2000 (870 000).
c L represents the length of the time series (993 weeks); estimated value was rounded to the nearest week and the corresponding calendar date of that week is given.