Viral bronchiolitis is a common worldwide disease of infants and young children. It is a significant cause of hospitalisation in infancy. In the year 2002–3, 0.1% of all hospital bed days in England were for acute bronchiolitis with a mean length of stay of 2.7 days,¹ and in a study in one UK region the incidence of bronchiolitic related admission was 30.8 per 1000 infants.²

PATHOPHYSIOLOGY

The underlying pathophysiology is inflammation of the small airways (bronchioles). Infection of the bronchiolar and ciliated epithelial cells produces increased mucous secretion, cell death and sloughing, followed by a peribronchiolar lymphocytic infiltrate and submucousal oedema.³ This combination of debris and oedema results in distal airway obstruction. During expiration, the additional dynamic narrowing produces disproportionate airflow decrease and air trapping. The effort of breathing is increased due to increased end expiratory lung volume and decreased lung compliance.³ Recovery of pulmonary epithelial cells occurs after 3–4 days, but cilia do not regenerate for approximately two weeks.³ The debris is cleared by macrophages.

EPIDEMIOLOGY

Fifty to ninety per cent of bronchiolitis is caused by respiratory syncitial virus (RSV) infection.⁴ RSV is a negative-sense, enveloped RNA virus that is unstable in the environment, surviving only a few hours on environmental surfaces. RSV is spread from respiratory secretions through close contact with infected persons or contact with contaminated surfaces or objects. Infection can occur when infectious material contacts mucous membranes of the eyes, mouth, or nose, and possibly through the inhalation of droplets generated by a sneeze or cough.⁵ RSV infects virtually all infants and young children in the first 3 years of life with a peak incidence of hospitalised patients between 2–6 months of life.⁶ During their first RSV infection, between 25–40% of infants and young children have signs or symptoms of …