In a typical case, an infant under two years of age develops cough, wheeze, and shortness of breath over one or two days. 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.

Causes

The term usually refers to acute viral bronchiolitis, a common disease in infancy. This is most commonly caused by respiratory syncytial virus^[1] (RSV, also known as human pneumovirus). Other viruses which may cause this illness include metapneumovirus, influenza, parainfluenza, coronavirus, adenovirus, and rhinovirus.

Studies have shown there is a link between voluntary caesarean birth and an increased prevalence of bronchiolitis. A recent study by Perth's Telethon Institute for Child Health Research has shown an 11% increase in hospital admissions for children delivered this way.^[2]

Diagnosis

The diagnosis is typically made by clinical examination. Chest X-ray is sometimes useful to exclude pneumonia, but not indicated in routine cases.^[3]

Testing for the specific viral cause can be done but has little effect on management and thus is not routinely recommended.^[3] RSV testing by direct immunofluorescence testing on nasopharyngeal aspirate had a sensitivity of 61% and specificity of 89%.^[4] Identification of those who are RSV-positive can help for: disease surveillance, grouping ("cohorting") people together in hospital wards 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).

Infant with bronchiolitis between the age of two and three months have a second infection by bacteria (usually a urinary tract infection) less than 6% of the time.^[5]

Prevention

Prevention of bronchiolitis relies strongly on measures to reduce the spread of the viruses that cause respiratory infections (that is, handwashing, and avoiding exposure to those symptomatic with respiratory infections). In addition to good hygiene an improved immune system is a great tool for prevention. One way to improve the immune system is to feed the infant with breast milk, especially during the first month of life^[6]. Immunizations are available for premature infants who meet certain criteria (some cardiac and respiratory disorders) such as Palivizumab (a monoclonal antibody against RSV). Passive immunization therapy requires monthly injections every winter.

Management

Treatment and management of bronchiolitis is usually focused on the symptoms instead of the infection itself (supportive therapies) since the infection will run its course and complications are typically from the symptoms themselves.^[7]

Inhaled epinephrine

Nebulized and inhaled epinephrine (both racemic and levo(1)-epinephrine) has been shown to decrease hospitalization rates^[8][9]. Sometimes inhaled hypertonic saline is used.

Inhaled hypertonic saline

Inhaled hypertonic saline (3%) appears to be effective in improving clinical outcomes and shortening the duration of hospital stay^[3].

Other medications

Currently other medications do not yet have evidence to support their use^[9].

Epidemiology

90% of the patients are aged between 1 and 9 months old. Bronchiolitis is the most common cause of hospitalization up to the first year of life. It is epidemic in winters.