Common Cause of Bronchiolitis
Respiratory syncytial virus (RSV) is the most common cause of bronchiolitis in infants under 2 years of age. 1
Epidemiology of RSV as Primary Pathogen
- RSV accounts for the majority of bronchiolitis cases, with approximately 90% of children becoming infected within their first 2 years of life 2
- Up to 40% of infants infected with RSV will develop lower respiratory tract infection during their initial exposure 1, 2
- The peak incidence occurs between December and March in North America, though regional variations exist 2
- RSV bronchiolitis results in more than 90,000 hospitalizations annually in the United States 1
Other Viral Etiologies
While RSV predominates, several other viruses can cause the identical clinical presentation of bronchiolitis:
- Human metapneumovirus is recognized as a significant causative agent 1, 2
- Influenza virus can produce bronchiolitis 1, 2
- Adenovirus is identified as a causative pathogen 1, 2
- Parainfluenza viruses contribute to bronchiolitis cases 1, 2
- Human rhinovirus and coronavirus have been identified as etiological agents, with rhinovirus potentially associated with less severe acute disease but increased risk of subsequent wheezing 3, 4
Clinical Implications
- All these viruses produce the same constellation of symptoms—acute inflammation, edema and necrosis of epithelial cells lining small airways, increased mucus production, and bronchospasm—making clinical differentiation impossible 1
- Viral testing is not routinely recommended for diagnosis, as it does not change management and is useful only for cohort and quarantine purposes 3
- RSV infection does not confer permanent immunity, with reinfections occurring throughout life 1, 2
Important Caveat
The mortality from RSV has decreased dramatically over time, from approximately 4,500 deaths annually in 1985 to around 390 deaths by 1999, reflecting improved supportive care 1, 2