Overview of bronchiolitis.

Respiratory syncytial virus RSV, a nonsegmented, single stranded ribonucleic acid virus, infects one-half of all infants within the first year of life. Respiratory syncytial virus possesses pathogenetic qualities that may be attributed to the interplay of viral and host-specific factors including virus strains of different virulence, size of the inoculum, family history of asthma or airway hyper-reactivity and immunologic anomalies of the host. Inflammatory cell recruitment and activation occur in response to RSV infection of epithelial cells.