Table 3. The impact of extrinsic or intrinsic host factors associated with supershedding in avian-virus systems for which data were available (test statistics are shown for the whole model, and odds ratios with 95% confidence intervals, (CI) are shown only for selected factors (statistically significant factors are shown in bold text)).

Avian – Virus System	Extrinsic Factor	Intrinsic Factor	Interaction	n	χ2	P Value	Odds Ratio (95% CI)
Chicken – WNV	CORT	Sex	CORT×Sex	37	17.33	0.001	320610 (NE‡)
Kestrel – AIV (oral)	Virus Dose	Sex	Dose×Sex	16	2.02	0.568
Kestrel – AIV (cloacal)	Virus Dose	Sex	Dose×Sex	16	3.34	0.342
Dunlin – AIV (cloacal)	Virus Dose	–	–	20	0.115	0.735
Dunlin – AIV (oral)	Virus Dose	–	–	17	0.267	0.606
Catbird – EEEV	–	Sex	–	59	0.002	0.963
Catbird – WNV	–	Sex	–	59	0.429	0.513
Catbird – WNV	–	Migratory	–	17	0.018	0.893
Cardinal – WNV	CORT	Sex	CORT×Sex	19	0.046	0.997
Mallard – AIV	Food*	Sex	Food×Sex	40	4.87	0.181	4.38 (0.85–33.25)
Starling – AIV	–	Sex	–	36	1.789	0.181
HOSP† – AIV	–	Age, Sex	–	36	0.702	0.704

Notes:

^*, Normally fed versus food-restricted mallards (10 & 20% body condition reduction, [31], χ² = 3.12, df = 1, P = 0.077.

^†, House sparrow.

^‡, Not estimable because the denominator was zero (i.e., no control treated birds were supershedders).