Bronchiolitis is the most common disease of the lower respiratory tract during the first year of life. It usually presents with cough with increased work of breathing, and it often affects a baby's ability to feed. In primary care, the condition may often be confused with a common cold, though the presence of lower respiratory tract signs (wheeze or crackles on auscultation) in a baby in mid‑winter would be consistent with this clinical diagnosis. The symptoms are usually mild and may only last for a few days, but in some cases the disease can cause severe illness.

There are several individual and environmental risk factors that can put babies and children with bronchiolitis at increased risk of severe illness. These include congenital heart disease, neuromuscular disorders, immunodeficiency and chronic lung disease.

The management of bronchiolitis depends on the severity of the illness. In most babies and children bronchiolitis can be managed at home by parents or carers.

Approximately 1 in 3 babies will develop clinical bronchiolitis in the first year of life and 2% to 3% of all babies will need to be admitted to hospital. In 2011/12 in England, there were 30,451 secondary care admissions for the management of bronchiolitis. It is uncommon for bronchiolitis to cause death. In 2009/10 in England, there were 72 recorded deaths of babies and children within 90 days of hospital admission for bronchiolitis.

Bronchiolitis is associated with an increased risk of chronic respiratory conditions, including asthma, but it is not known if it causes these conditions.

The guideline covers babies and children with bronchiolitis but not those with other respiratory conditions, such as recurrent viral induced wheeze or asthma.