Table 2. Parameters of linear regression models of the association between norovirus outbreaks and BioSense emergency department diarrhea subsyndrome visit data, by state, United States, January 2007–April 2010*.
| State no. | Total no. emergency department visits/mo | Norovirus,† β1, × 10−4 (95% CI) | p value‡ | R |
|---|---|---|---|---|
| 1 | 273,218 | 2.86 (1.72 to 4.00) | <0.0001 | 0.858 |
| 2§ | 137,584 | 6.91 (4.60 to 9.22) | <0.0001 | 0.809 |
| 3¶ | 66,597 | 3.79 (2.74 to 4.83) | <0.0001 | 0.832 |
| 4¶ | 21,684 | 7.06 (0.73 to 13.40) | 0.0298 | 0.637 |
| 5¶ | 5,214 | 2.18 (1.57 to 2. 78) | <0.0001 | 0.800 |
| 6§¶ | 836 | 0.53 (−8.77 to 9.84) | 0.9082 | 0.133 |
*Emergency department chief complaint–based visits for diarrhea subsyndrome as a monthly proportion of all visits regressed on norovirus surveillance data, rotavirus antigen test data, and time variable. Intercept for each model p<0.0001. †Suspected and confirmed norovirus outbreaks. ‡By t test. ¶Time variable not significant in model (p>0.05). §Proportion of rotavirus tests positive variable not significant in model (p>0.05).