Causes of Bronchiolitis
Causes of bronchiolitis are almost always viral, with respiratory syncytial virus (RSV) being the most common trigger. The leading causes of bronchiolitis include RSV, influenza virus, rhinovirus, adenovirus, and parainfluenza virus. These viruses are easily spread through droplets in the air when someone coughs or sneezes, or through direct contact with contaminated surfaces.
RSV accounts for the majority of bronchiolitis cases, especially in babies under 12 months old. RSV is highly contagious and spreads quickly in crèches, households, and hospitals. It can live on surfaces such as toys, bedding, and doorknobs for hours, making hygiene and handwashing crucial in preventing transmission.
Other viruses like influenza and rhinovirus, which cause flu and the common cold respectively, can also infect the lower airways and lead to bronchiolitis, particularly in children who already have a weakened immune system.
Babies and toddlers are more vulnerable because their airways are smaller, meaning even a little swelling or mucus can block airflow. Those born prematurely or with conditions such as congenital heart disease, asthma, or chronic lung problems are at higher risk of severe bronchiolitis.
Causes of bronchiolitis
Exposure to tobacco smoke, overcrowded living conditions, and lack of breastfeeding can also increase the risk. Seasonal outbreaks are common during the colder months, and siblings or caregivers with a common cold can unknowingly pass the virus to the child.
Although bronchiolitis mostly affects infants and toddlers, older children and adults can contract the viruses that cause it — but in them, it usually results in only mild cold symptoms.
Understanding the causes of bronchiolitis helps in early recognition and prevention, particularly for high-risk babies. Avoiding sick contacts, maintaining good hygiene, and keeping environments smoke-free are key steps in reducing transmission.
[Next: Symptoms of Bronchiolitis →]
