Childhood Asthma and Viral Infections
A study, in America, by Wu et al found that Bronchiolitis during infancy is associated with an increased risk of childhood asthma.
They studied the risk for development of childhood asthma in relation to the child's age at the onset of the peak of the winter viral bronchiolitis season. In each case, the highest susceptibility was at an age of about 4 months at the onset of the winter virus peak.
They concluded that having clinically significant bronchiolitis at any age during infancy was associated with an increased risk of developing high-risk childhood asthma no matter what the infant's age at the time of the illness. Delay of exposure or prevention of winter viral infection during early infancy could prevent asthma.
It is not clear whether bronchiolitis causes asthma or serves as a marker for those genetically predisposed to develop the disease.
Evidence of a causal role of winter virus infection during infancy in early childhood asthma.
Wu P, Dupont WD, Griffin MR, Carroll KN, Mitchel EF, Gebretsadik T, Hartert TV
Am J Respir Crit Care Med. 2008 Dec 1;178(11):1097-8.