Bronchiolitis
Bronchiolitis is inflammation of the bronchioles, the smallest air passages of the lungs.
The term usually refers to acute viral bronchiolitis, a common disease in infancy. This is most commonly caused by respiratory syncytial virus (RSV, also known as human pneumovirus). (J21.0)
Other viruses which may cause this illness include metapneumovirus, influenza, parainfluenza, coronavirus, adenovirus, and rhinovirus.
In a typical case, an infant under twelve months of age develops cough, wheeze, and shortness of breath over one or two days. The diagnosis is made by clinical examination. Chest X-ray is sometimes useful to exclude pneumonia, but not indicated in routine cases.
Testing for specific viral cause (e.g. RSV by nasopharyngeal aspirate) is common, but has little effect on management. RSV infection usually indicates more significant disease than other viruses. Identification of RSV-positive patients can be helpful for:
disease surveillance
grouping ("cohorting") patients together in hospital wards as to prevent cross infection
predicting whether the disease course has peaked yet
reducing the need for other diagnostic procedures (by providing confidence that a cause has been identified).
The infant may be breathless for several days. After the acute illness, it is common for the airways to remain sensitive for several weeks, leading to recurrent cough and wheeze. (There is a possible link with later asthma: possible explanations are that bronchiolitis causes asthma by inducing long term inflammation, or that children who are destined to be asthmatic are more prone to develop bronchiolitis.)