We analyzed polymorphisms of IL-10 -1082 G/A, IL-18 -137 G/C, TLR4 +896 A/G, and IFNG +874 T/A in 139 infants under 6 months of age hospitalized with bronchiolitis and 400 unselected blood donors. Causative viruses were determined by PCR. Infants with bronchiolitis associated with a virus other than respiratory syncytial virus (N = 18), were more often IL-10 -1082 allele G non-carriers, that is, homozygous for allele A (AA) than controls (66.7% vs. 28.0%, P < 0.0001). Infants with RSV bronchiolitis did not differ from controls. This finding suggests a different pathogenic mechanism for RSV bronchiolitis as compared with wheezing associated with other viral infections, for example, rhinovirus in infants under 6 months of age.

Currently available drugs were not effective in relieving cough symptoms. Salbutamol inhalations could relieve the symptoms of wheezing bronchitis and should be administered via a holding chamber. Nebulised adrenaline or inhaled or oral glucocorticoids did not reduce hospitalisation rates or relieve symptoms in infants with bronchiolitis and should not be routinely used.

After bronchiolitis at less than 6 months of age, the risk of doctor-diagnosed asthma at 11-13 years was about twice that of the general Finnish population. Maternal asthma was the only independently significant early-life risk factor for current asthma at 11-13 years of age.

Though reduced lung function and increased airway reactivity were rather common, evidence for persistent lung function reduction was rare, less than 1%, at preschool age in children hospitalized for bronchiolitis caused mainly by respiratory syncytial virus at age less than 6 months.

Children with RV- or RSV-induced wheezing in early childhood have an increased risk for asthma and lung function abnormalities in adulthood.

Reduced FEV1 after bronchodilation was found in early adolescence after infant bronchiolitis, suggesting irreversible bronchial obstruction.

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Cytokine and TLR4 polymorphisms and their association with the infection history of 129 children hospitalized for bronchiolitis during the first 6 months of life were analyzed. The carriers of IFNG +874 T/A allele A had fewer infections and use of inhaled corticosteroids and the carriers of TLR4+896 A/G allele G were more likely to need tympanostomy than noncarriers.