Table 3.

Multivariate relationships between food vehicles and outcomes of attack rate and genogroup for published norovirus outbreaks.

	Attack Rate (n=91) δ			Genogroup (n=120) ** δ
				GI		Both GI and GII
Variable γ	Beta	SE	p value	OR	95% CI	OR	95% CI
Food Vehicles
Produce	Reference Category			Reference Category		Reference Category
Shellfish	16.10	9.41	0.09	0.14*	0.02–0.96	15.14*	1.64–139.86
Ready to eat	−6.69	8.25	0.42	0.50	0.12–2.15	0.14 φ	0.01–3.86
Season
Winter	Reference Category			Reference Category ⱡ		Reference Category ⱡ
Spring	−0.60	5.61	0.92	1.46	0.39–5.44	1.28	0.47–3.51
Summer	3.96	8.43	0.64
Fall	−6.12	9.53	0.52
Hemisphere
Northern	Reference Category			Reference Category		Reference Category
Southern	−39.8*	9.40	<0.01	2.30	0.13–39.33	0.16*	0.02–0.997
Setting
Foodservice	Reference Category			ℓ	ℓ	ℓ	ℓ
Leisure	−17.76	9.76	0.07	ℓ	ℓ	ℓ	ℓ
School/Daycare	28.45	17.05	0.10	ℓ	ℓ	ℓ	ℓ
Healthcare	−26.67	13.73	0.06	ℓ	ℓ	ℓ	ℓ

^δAttack rate estimates adjusted for genogroup and vice versa.

^**Reference category for genogroup is GII.

^γItalic covariates are eliminated by backward elimination (α=0.05) without confounding covariate estimates.

^*Significant beta or odds ratio estimate.

^φEstimates obtained using logistic model and Firth correction.

^ⱡSpring, summer, and fall are collapsed to obtain valid estimates.

^ℓVariables not included due to sparse data.