Table 3.

Mean Ct Values Estimated by the Multivariate Mixed-Effect Poisson Regression Model by Timing of Specimen Collection, Outbreak Characteristics, and Rotavirus Coinfection (Model 2–4)

Characteristics	Number of Specimens	Mean Estimate	(95% CI)	P Value
Specimen collection (Model 2)				<.0001
Before symptom onset	2	30.1	(22.3–40.5)
Date of symptom onset	2270	24.9	(21.9–28.4)
1–3 days after symptom onset	2738	24.5	(21.4–27.9)
4–7 days after symptom onset	1184	25.0	(21.9–28.5)
8–14 days after symptom onset	283	27.3	(23.9–31.2)
15–30 days after symptom onset	38	27.5	(23.7–31.8)
>30 days after symptom onset	12	26.4	(22.1–31.5)
Transmission mode (Model 3)				.002
Environmental	8	26.3	(22.6–30.5)
Foodborne	852	22.6	(21.3–24.0)
Person-to-person	3966	23.3	(22.0–24.7)
Waterborne	13	23.0	(20.3–26.1)
Unknown/other modes	1150	22.8	(21.5–24.1)
Outbreak setting (Model 3)				<.0001
Child care facility	93	25.0	(23.1–27.0)
Correctional facility	83	23.1	(21.3–25.1)
Cruise ships	76	20.8	(19.1–22.7)
Food facility	607	24.0	(22.4–25.7)
Healthcare facility	215	23.0	(21.3–24.7)
Long-term care facility	3862	23.5	(21.9–25.2)
School	347	24.5	(22.8–26.2)
Other setting	670	23.7	(22.1–25.3)
Unknown setting	36	24.8	(22.5–27.3)
Rotavirus (Model 4)				.3
Positive	54	29.2	(26.4–32.4)
Negative	719	28.3	(25.9–30.9)

Abbreviations: CI, confidence interval; Ct, cycle threshold.