Incidence, distribution, seasonality, and demographic risk factors of Salmonella Enteritidis human infections in Ontario, Canada, 2007–2009

Table 2 Risk factors for Salmonella Enteritidis infections in humans, Ontario, Canada, 2007–2009 (n = 1,932 cases)

Variable ^a)		IRR ^b)	95% CI ^c)	P-value ^d)
Year	2007	Reference	-	-
	2008	1.17	1.05-1.31	0.005
	2009	1.18	1.06-1.32	0.003
Season	Fall	Reference	-	-
	Spring	1.14	1.01-1.29	0.040
	Summer	1.06	0.93-1.20	0.377
	Winter	1.06	0.93-1.20	0.413
Age (years)	0-4	Reference	-	-
	5-9	0.64	0.52-0.78	< 0.001
	10-19	0.44	0.34-0.51	< 0.001
	20-29	0.51	0.43-0.60	< 0.001
	30-39	0.34	0.28-0.40	< 0.001
	40-49	0.31	0.26-0.37	< 0.001
	50-59	0.33	0.28-0.40	< 0.001
	≥ 60	0.31	0.26-0.37	< 0.001
Sex	Female	Reference	-	-
	Male	0.95	0.87-1.04	0.273
Intercept		0.00002	0.00002-0.00003	< 0.001

^a) Multi-level mixed-effects Poisson regression model using adaptive Gaussian quadrature. Public health unit (PHU) was included as a random intercept. Variance of PHU random effects = 0.074 [95% CI = 0.036-0.153]. Dependent variable: number of Salmonella Enteritidis cases by year, season, age group, sex, and PHU. Offset: natural log-transformed year-, age group-, sex-, and PHU-based population size estimates. ^b) IRR: Incidence rate ratio for categorical independent variables, in which the incidence rate (IR) in the category of interest was compared to the IR in the reference category. ^c) CI: Confidence interval of the IRR. ^d) Statistically significant at P ≤ 0.05.

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