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Causes
By Mayo Clinic staffBronchiolitis occurs when a virus enters the respiratory system and makes its way to the bronchioles, which are the smallest of the airways branching off the two main breathing tubes (bronchi) within your lungs. The viral infection makes the bronchi swell and become inflamed. As a result, mucus often collects in these airways, which can make it difficult for air to flow freely through your lungs.
In older children and adults, the resulting signs and symptoms are generally mild. But an infant's bronchioles are much narrower than are an adult's and are more easily blocked, leading to greater difficulty breathing.
The respiratory syncytial virus (RSV), a common virus, causes most childhood bronchiolitis cases. The rest are caused by other infectious agents, including viruses that cause the flu or the common cold.
Bronchiolitis is a contagious condition. You contract the virus just as you would a cold or the flu — through droplets in the air when someone who is sick coughs, sneezes or talks. You can also contract bronchiolitis by touching shared objects — such as utensils, towels or toys — and then touching your eyes, nose or mouth.
- In: Mandell GL, et al. Mandell, Douglas, and Bennett's Principles and Practice of Infectious Diseases. 76th ed. Philadelphia, Pa.: Churchill Livingstone Elsevier; 2009. Accessed Aug. 5, 2010.
- Piedra PA. Bronchiolitis in infants and children: Clinical features and diagnosis. http://www.uptodate.com/home/index.html. Accessed Aug. 5, 2010.
- Watts KD, et al. Wheezing, bronchiolitis, and bronchitis. In: Kliegman RM, et al. Nelson Textbook of Pediatrics, 18th ed. Saunders Elsevier; 2007. Accessed Aug. 5, 2010.
- Everard ML. Acute bronchiolitis and croup. Pediatric Clinics of North America. 2009;56:119.
- Seiden JA, et al. Bronchiolitis: An evidence-based approach to management. Clinical Pediatric Emergency Medicine. 2009;10:75.
- Hoecker JL (expert opinion). Mayo Clinic, Rochester, Minn. Aug. 8, 2010.
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