Overview
Bronchiolitis is an acute viral infection of the lower respiratory tract, affecting mainly infants under 2 years of age, with a peak between 3-6 months.
It is the most frequent lower respiratory infection in children within this age. It causes an obstruction of the wall of the bronchioles secondary to edema, mucus, and cellular debris; all of them, together with bronchospasm, increase the resistance of the small airways, leading to air trapping, overinflation, and, ultimately, atelectasis.
Respiratory Syncytial Virus (RSV) is the most common etiologic agent accounting for at least half of the cases. Other viruses detected in nasopharyngeal secretions from children hospitalized with bronchiolitis are rhinovirus, parainfluenza, human metapneumovirus (hMPV), bocavirus, coronavirus, influenza, and adenovirus, and coinfection has been described. There are no differences in the clinical presentation depending on the etiologic agent, although there can be some differences in the severity.
RSV is present worldwide, and 90% of the children will be infected in the first 2 years of life. It causes annual epidemics of bronchiolitis; the peak season varies amongst the countries depending on environmental and meteorological factors, but roughly occurs in wintertime and late spring: from November to March in the northern hemisphere, and from May to September in the southern hemisphere.
To date, there is no etiologic treatment that shortens the course of the disease, being the cornerstone of the therapy the optimization of supportive and symptomatic measures.
As bronchiolitis has considerable morbi-mortality, several guidelines from different organisms are periodically published reviewing the best evidence to guide the clinicians in its management.