In the linked systematic review (doi:10.1136/bmj.d1714), Hartling and colleagues assess the efficacy and safety of bronchodilators and steroids, alone or combined, for the acute management of bronchiolitis.1 Bronchiolitis is the most common acute viral infection of the lower respiratory tract in the first year of life.2 Peak incidence occurs in the autumn and winter, with 10% of children being affected in their first year and 90% by age 2.3 Respiratory syncytial virus is the most common underlying cause, but several other viruses are also implicated. Worldwide, about 34 million episodes of respiratory syncytial virus associated bronchiolitis occur each year. Although it is generally a benign condition, 10% of affected children need to be admitted to hospital, and it has an overall mortality rate of 0.2-0.5%, with 99% of deaths occurring in developing countries.2 Risk factors for disease severity include prematurity, chronic lung disease, and congenital heart disease.4

Bronchiolitis is usually defined as the first episode of wheezing (North America) or crackles (United Kingdom) with clinical evidence of viral infection (such as coryza or fever) in a child under 12-24 months of …