Bronchiolitis · What Is It, Transmission, Symptoms, Treatment, and More

The pathogens responsible for bronchiolitis spread from one person to another. Usually, pathogens spread when infected people cough, sneeze, or even talk, releasing tiny saliva droplets in the air. These droplets can then infect another person when they land on that person’s mouth, nose, or eyes.

Pathogens can also spread through contact transmission. This refers to saliva droplets that land on object surfaces such as door handles and then spread to the next person that touches these surfaces and touches their eyes, nose, or mouth.  

After the pathogen-containing droplets spread to the next person, infection can result when the amount of virus is sufficient or the host immune system is impaired. At the bronchioles, pathogens can infect and kill respiratory epithelial cells, triggering an inflammatory reaction. This causes surrounding epithelial cells to secrete more mucus, forming plugs of mucus and dead cells, and ultimately blocking the airways. 

The initial clinical presentation of bronchiolitis is similar to that of the common cold, with symptoms like congestion, runny nose, cough, sore throat, and mild fever. Physical exam findings typically include wheezing or crackles. More severe cases can develop trouble breathing or hypoxia (i.e., low oxygen levels).  

Infants and young children can also experience signs of difficulty breathing, such as tachypnea (rapid breathing), nasal flaring, grunting sounds, intercostal retractions, and even apnea, which are short periods of time where breathing completely stops. In addition, infants and young children can be at increased risk of dehydration, as respiratory distress can lead to decreased fluid intake, as well as increased fluid loss due to fever and tachypnea (rapid breathing). 

The diagnosis of bronchiolitis is mostly clinical, based on the presenting symptoms, the age of the child, and the time of the year. Identification of the exact pathogen causing the disease is not necessary for treatment, but can be done through a nasopharyngeal swab. This is done by swabbing epithelial cells from the nasopharynx and looking for the presence of viral antigens.  

Chest X-ray is not routinely used, but is recommended in severe cases of bronchiolitis to rule out bacterial pneumonia. Typical X-ray findings of bronchiolitis include fullness of the central, perihilar region of the lung.