Last updated on: July 23rd, 2021

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Clinicals - History


Bronchiolitis is a viral lower respiratory tract infection characterized by obstruction of the small airways. Respiratory syncytial virus is responsible for most cases, but influenza, adenovirus, rhinovirus, parainfluenza and human metapneumovirus can cause a similar clinical picture. Coinfection with multiple viruses can occur.


Fever is a nonspecific, early sign.


While nonspecific, cough is a common symptom in bronchiolitis.


While nonspecific, rhinorrhea is a common finding in bronchiolitis, especially early on.

Difficulty feeding

Respiratory distress, rhinorrhea and nasal congestion may adversely affect feeding.

Respiratory distress

Signs of respiratory distress may occur after the prodrome. There may be increased respiratory rate and visible retractions, nasal flaring, and/or grunting.


There appears to be a relationship between a bronchiolitis diagnosis and apneic episodes. There does not appear to be an association with sudden unexplained infant death.


The death rate from bronchiolitis is low and falling, but this can occur due to respiratory failure.

Risk factor: winter season

In temperate climates, bronchiolitis is more prevalent during the winter months. There is less of a seasonal preponderance in tropical climates, and suspicion for the disease should be present year-round.

Much of this is related to the seasonal prevalence of the most common pathogen, respiratory syncytial virus (RSV).

Risk factor: young age

Viral bronchiolitis is more common in children under 2 years of age—especially during the first year of life.

Risk factor: prematurity

Premature infants are at higher risk for hospitalization due to bronchiolitis.

Risk factor: pre-existing chronic disease

Infants with chronic heart or lung disease or immunodeficiency may be at higher risk for severe bronchiolitis.

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