TABLE 5.

Factors associated (P ≤ 0.25) with pulmonary infection on univariate analysis

Factor	Category	No. of cases	Odds ratio	95% confidence interval	P value
Farm	Farm O	18/20 (90%)	0.14	0.01, 1.67	<5 × 10−5
	Farm W	29/31 (94%)	0.23	0.02, 2.64
	Farm Ma	63/64 (98%)	1
	Other	61/89 (69%)	0.03	0.005, 0.26
Age	Linear/10 days	184	0.76	0.65, 0.90	0.001
Age	<30 days	11/11 (100%)	1,010	<10−6, >106	0.005
	30–39 days	38/39 (97%)	10.5	1.24, 88.6
	40–49 days	46/52 (88%)	2.11	0.67, 6.72
	50–59 daysa	29/37 (78%)	1
	60–69 days	14/18 (78%)	0.97	0.25, 3.76
	70–89 days	10/15 (67%)	0.55	0.15, 2.08
	≥90 days	8/12 (67%)	0.55	0.13, 2.31
Date of birth	August	27/36 (75%)	0.81	0.26, 2.49	0.20
	Sept. 1–15	24/26 (92%)	3.23	0.61, 17.1
	Sept. 16–30	25/29 (86%)	1.68	0.44, 6.46
	Oct. 1–15a	26/33 (79%)	1
	Oct. 16–31	25/27 (93%)	3.36	0.64, 17.8
	Nov. 1–15	19/20 (95%)	5.11	0.58, 45.0
	After Nov. 15	10/13 (77%)	0.90	0.19, 4.17
Year of birth	1991	23/26 (88%)	0.94	0.21, 4.27	0.23
	1992	13/15 (87%)	0.79	0.14, 4.58
	1993	26/28 (93%)	1.59	0.29, 8.78
	1994a	41/46 (89%)	1
	1995	29/36 (81%)	0.51	0.15, 1.75
	1996	26/33 (79%)	0.45	0.13, 1.58
	1997	9/15 (60%)	0.18	0.05, 0.73
	1998	4/5 (80%)	0.49	0.05, 5.27

^aThis category was the reference category.