Bronchiolitis usually occurs during the first ___ of life.

Bronchiolitis is a common respiratory illness that primarily affects infants and young children, particularly those under the age of 2. It is typically caused by viral infections, with respiratory syncytial virus (RSV) being the most common culprit. The first two years of life are critical for the development of the respiratory system, and during this time, infants are particularly vulnerable to infections that can lead to bronchiolitis.

The peak incidence of bronchiolitis typically occurs in children from 2 to 6 months of age, but the condition can still occur in children up to 2 years old. Beyond the age of 2, the incidence of bronchiolitis significantly decreases as the child's immune system becomes more robust and their airways become larger and more developed, making them less susceptible to the same viral infections that lead to bronchiolitis in younger children.

Therefore, the correct choice truly reflects the age spectrum in which bronchiolitis is most relevant, indicating that it is primarily recognized and diagnosed within the first two years of life, aligning with the typical clinical presentation and outcomes associated with this condition.