A most common cause of Bronchiolitis is?
**Core Concept**
Bronchiolitis is a common respiratory illness affecting infants, characterized by inflammation and obstruction of the small airways. The underlying cause is often related to viral infections. **Respiratory syncytial virus (RSV)** is a key player in this condition.
**Why the Correct Answer is Right**
The correct answer is related to the most common viral cause of bronchiolitis. **RSV** infects the epithelial cells lining the small airways, leading to cell death, inflammation, and increased mucus production, which obstructs the airways. This process is mediated by the immune response to the virus.
**Why Each Wrong Option is Incorrect**
**Option A:** Influenza can cause respiratory illness but is not the most common cause of bronchiolitis.
**Option B:** Adenovirus can cause a range of respiratory symptoms but is less commonly associated with bronchiolitis than RSV.
**Option D:** Other viruses and bacteria can cause similar symptoms but are not the primary cause.
**Clinical Pearl / High-Yield Fact**
Remember, **RSV** is the most common cause of bronchiolitis, especially in infants under two years of age.
**Correct Answer:** D. Respiratory Syncytial Virus