bronchiolitis

The airways branch like a tree into ever-smaller twigs; the tiniest of these, the bronchioles, are no wider than a thread in a baby. Bronchiolitis is what happens when a virus inflames these tiny twigs, clogging them with swelling and mucus. Because an infant's airways are already so narrow, even a little extra swelling makes breathing fast, wheezy and hard work.

Bronchiolitis is a viral inflammation of the small airways that chiefly affects young infants, typically under one year, with most cases caused by respiratory syncytial virus during winter outbreaks. It usually begins like a cold with a runny nose and cough, then over a day or two progresses to fast breathing, wheeze, fine crackles and difficulty feeding as the baby works harder to breathe.

Care is mainly supportive: keeping the baby fed and hydrated, clearing the nose, and giving oxygen if levels drop; most infants recover at home over one to two weeks. There is no good evidence that antibiotics, bronchodilators or steroids help typical bronchiolitis, so they are generally avoided. Warning signs that prompt hospital care include poor feeding, marked breathing effort, pauses in breathing or low oxygen.

Bronchiolitis is sometimes confused with a first attack of asthma because both cause wheeze in a young child, but in genuine viral bronchiolitis the wheeze comes from inflamed clogged tubes rather than the reversible muscle tightening of asthma, which is why asthma medicines often do not help.