Table 2.

Unadjusted and adjusted multiple linear regression coefficients modeling primary attack rate as a function of potential NoV outbreak risk factors.

Variable	Unadjusted*			n	Adjusted, no multiple transmission routes (n=233)			Adjusted, with multiple transmission routes (n=339)
	Beta	Std Error	P-value		Beta	Std Error	P-value	Beta	Std Error	P-value
Intercept					1470.05	913.86	0.11	257.92	754.32	0.73
Transmission				309
Foodborne	29.48†	4.11	<0.0001		10.53	7.20	0.15	5.48	3.99	0.17
Waterborne	18.18†	5.76	<0.01		13.40	8.22	0.10	7.61	5.38	0.16
Environmental	7.63	12.22	0.53		11.76	15.66	0.45	−3.38	5.29	0.52
Person-to-Person	Ref.	-	-		Ref.	-	-	Ref.	-	-
Setting				469
Foodservice	22.07†	4.35	<0.0001		14.23	8.37	0.09	14.17†	5.96	0.02
Healthcare	−10.93†	4.62	0.02		0.68	9.35	0.94	−3.11	6.58	0.64
Leisure	0.72	4.88	0.88		−1.34	8.84	0.88	−3.01	5.92	0.61
Other	9.77	5.39	0.07		−2.61	9.28	0.78	−0.42	6.79	0.95
School/Daycare	Ref.	-	-		Ref.	-	-	Ref.	-	-
Outbreak Year	0.01	0.01	0.31	508	−0.72	0.46	0.12	−0.11	0.38	0.76
Season				475
Winter	2.75	3.89	0.48		6.03	5.08	0.24	9.90†	3.56	<0.01
Spring	5.74	4.34	0.19		0.19	5.51	0.97	7.24	4.13	0.08
Summer	−0.47	5.09	0.93		−1.31	5.79	0.82	2.10	4.22	0.62
Fall	Ref.	-	-		Ref.	-	-	Ref.	-	-
Action to stop transmission				508
Described in article	−8.27†	3.45	0.02		−6.53	4.46	0.14	2.61	3.16	0.41
Not described	Ref.	-	-		Ref.	-	-	Ref.	-	-
Genogroup				430
Genogroup II	−2.83	4.26	0.51		0.33	5.35	0.95	−3.69	4.24	0.39
Both GI and GII	11.17†	5.34	0.04		5.63	6.04	0.35	−0.21	4.95	0.97
Genogroup I	Ref.	-	-		Ref.	-	-	Ref.	-	-
Genogroup, by cluster‡				362
GII non cluster 4	0.97	4.27	0.82
GII cluster 4	−16.16†	4.27	0.0002
Both GI and GII	7.66	5.29	0.15
GI	Ref.	-	-
Adjusted R2						0.14			0.15

^*Unadjusted analyses excluded outbreaks with multiple modes of transmission.

^†p < 0.05.

^‡GII outbreaks with no cluster data were excluded from unadjusted model.