bronchiolitis

Bronchiolitis is what a respiratory virus does to the lower airways of a very young child. The UK's National Institute for Health and Care Excellence describes it as the most common disease of the lower respiratory tract in the first year of life, presenting with a cough and increased work of breathing, and often interfering with a baby's ability to feed. It occurs in children under 2 and most commonly in the first year, peaking between 3 and 6 months of age.

Most cases are mild and are managed at home. NICE estimates that roughly 1 in 3 babies develops bronchiolitis in the first year of life, and that 2 to 3 percent of all babies need to be admitted to hospital for it. Death is uncommon. Congenital heart disease, chronic lung disease, neuromuscular disorders and a weakened immune system all raise the risk of severe illness.

Respiratory syncytial virus is the usual cause, and bronchiolitis is the reason RSV matters more in infancy than at any other age. The infection is hard to tell apart from a common cold in general practice, so the diagnosis rests on signs lower down in the chest, such as wheeze or crackles heard through a stethoscope in a baby in mid winter.