Signs and symptoms
Bronchiolitis typically presents in children under two years old and is characterized by a constellation of respiratory symptoms that consists of fever, rhinorrhea, cough, wheeze, tachypnea and increased work of breathing such as nasal flaring or grunting that develops over one to three days. Crackles or wheeze are typical findings on listening to the chest with a stethoscope. The child may also experience apnea, or brief pauses in breathing. After the acute illness, it is common for the airways to remain sensitive for several weeks, leading to recurrent cough and wheeze. Some signs of severe disease include:
increased work of breathing (such as use of accessory muscles of respiration, rib & sternal retraction, tracheal tug)
severe chest wall recession (Hoovers sign)
presence of nasal flaring and/or grunting
increased respiratory rate above normal
hypoxia (low oxygen levels)
cyanosis (bluish skin)
lethargy and decreased activity
poor feeding (less than half of usual fluid intake in preceding 24 hours)
history of stopping breathing

Causes
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). Other agents that cause this illness include human metapneumovirus, influenza, parainfluenza, coronavirus, adenovirus, rhinovirus and mycoplasma. Risk factors
Children are at an increased risk for progression to severe respiratory disease if they have any of the following additional factors:
Preterm infant (gestational age less than 37 weeks)
Younger age at onset of illness (less than 3 months of age)
Congenital heart disease
Immunodeficiency
Chronic lung disease
Neurological disorders
Tobacco smoke exposure

Diagnosis
The diagnosis is typically made by clinical examination.
Guidelines recommend exclusive breastfeeding for infants for the first 6 months of life.Palivizumab, a monoclonal antibody against RSV, can be administered to prevent bronchiolitis to infants less than one year of age that were born very prematurely or that have underlying heart disease or chronic lung disease of prematurity. Passive immunization therapy requires monthly injections during winter. Otherwise healthy premature infants that were born after a gestational age of 29 weeks should not be administered palivizumab as the harms outweigh the benefits. Passive protection through the administration of other novel monoclonal antibodies is also under evaluation.Immunizations for RSV are being developed but none are available currently outside of clinical trials.Tobacco smoke exposure has been shown to increase both the rates of lower respiratory disease in infants, as well as the risk and severity of bronchiolitis. Tobacco smoke lingers in the environment for prolonged periods and on clothing even when smoking outside the home. Guidelines recommend that parents be fully educated on the risks of tobacco smoke exposure on children with bronchiolitis. Management
Treatment of bronchiolitis is usually focused on the hydration and symptoms instead of the infection itself since the infection will run its course and complications are typically from the symptoms themselves. Without active treatment, half of cases will go away in 13 days and 90% in three weeks. Children with severe symptoms, especially poor feeding or dehydration, may be considered for hospital admission. Oxygen saturation under 90%-92% as measured with pulse oximetry is also frequently used as an indicator of need for hospitalization.