Clinical and demographic characteristics
During the study period, 3793 patients were eligible and 3168 subjects (83.5%) were included in the final cohort (Figure 1). The median age at enrollment was 3.5 months, 1912 subjects (60%) were male, median birth weight was 3 kilograms, median gestational age was 40 weeks, and 28% of children were delivered by C-section11. Most subjects (77%) had exposure to household smoke, 84% were breastfed, and 2% attended daycare. Fourteen percent of subjects had an atopic mother with asthma, allergic rhinitis, or eczema, 3% had maternal asthma, 23% had a family history of asthma, and 6% had a personal history of atopy. Median length of hospital stay was 5 days, 1013 subjects (32%) received oxygen supplementation during hospitalization, 284 (9%) were admitted to the ICU and 111 (4%) were on mechanical ventilation during hospitalization 11. Overall, 2581 (81.5%) had at least one-virus detected, with 944/2581 (37%) having at least one virus codetected, and 1757 subjects (55%) had wheezing diagnosed by a physician (Figure 1).
Wheezing and non-wheezing subjects
On univariable analysis, children with wheezing were older; more likely to have UMCs; personal history of RAD, allergic rhinitis, and atopy; family history of asthma; receive oxygen; have a shorter LOS, but less likely to have a history of breastfeeding compared to non-wheezing subjects (Table 1). There were no differences in smoke exposure, prematurity, maternal history of atopy or ICU admission between the two groups (Table 1).
At least one virus was detected in 2581 (81%) of all subjects. In the wheezing group, viruses were detected in 1540 (88%) subjects, compared to 1041 (74%) in the non-wheezing group (p<0.005)(Figures 1). Figure 2 illustrates compared to non-wheezing subjects, those with wheezing had a higher frequency of RSV (53% vs. 33%), HMPV (11% vs. 6%), and any virus(88% vs. 74%). There was no difference in HRV detection between wheezing and non-wheezing subjects.