Table 2. Demographic features and clinical information of the patients included in the study.

Variable. n(%)	n (%)	Incidence rate- ratio (95% CI)	p
Age less than 6 month	277(66.4)	0.998 (0.9-0.9)	0.000
Male , n(%)	251(60.3)	0.048 (0.9-1.1)	0.218
Premature birth	81(19.4)	1.319 (1.1-1.4)	0.000
Comorbidities (CHD or neurological)	20(4.8)	1.787(1.5-2.0)	0.000
BPD	17(4.0)	1.037(0.8-1,2)	0.738
Atopy	17(4.0)	0.827(0.6-1.0)	0.123
Previously hospitalization by bronchiolitis	30(7.2)	0.750(0.6-0.9)	0.003
Exposure to cigarette smoking	49 (11.9)	1.040(0.9-1.1)	0.563
Exclusive maternal breastfeeding for at least six month	102(24.4)	0.627(0.5-1.0)	0.423
SpO2, median(ds)	89(0.2)	1.007(0.9-1.0)	0.055
O2 supportive , n(%)	347(83.4)	2.227(1.8-2.6)	0.000
Clinical & laboratory parameters
Fever	119(28.6)	0.834(0.7-0.9)	0.000
Chest indrawing	184(44.2)	1.416(1.2-1.5)	0.000
Tachypnea	48(13.3)	1.181(1.0-1.3)	0.018
Rhonchi	137(32.9)	0.777(0.7-0.8)	0.000
Crepitation	137(32.9)	1.088(0.9-1.1)	0.160
Abnormal X-ray *	109(26.3)	1.055(0.9-1.1)	0.277
Leucocytosis (> 15.000/mm3)	51(12.2)	1.179 (1.0-1.3)	0.010
RSV positive	200(48.4)	1.653(1.5-1.8)	0.000
Increased C-reactive protein (> 40 mg/lit.)	327(78.6)	0.849(0.7-0.9)	0.002

*Atelectasis (n=7), alveolar (n=16) or interstitial (n=48) infiltrates, hyperinflation (n=38) CHD : Congenital heart disease, BPD: Bronchopulmonary dysplasia, RSV: Respiratory syncytial virus