There are different causes of viral bronchiolitis and bronchiolitis obliterans.
Causes of viral bronchiolitis
Viruses that enter and infect the respiratory tract cause viral bronchiolitis. Viruses are microscopic organisms that can reproduce rapidly and challenge the immune system. The following are common types of viral infections that may cause bronchiolitis.
Respiratory syncytial virus (RSV)
RSV is the most common cause of bronchiolitis. RSV can affect people of all ages but is most likely to cause serious illness in children under 2 years old or in older adults with weakened immune systems. Most babies get RSV infections at least once by the time they turn 2 years old.
About 11 to 15 percent of infants experience bronchiolitis before they turn 1 year old, and about 1 in 200 children under 2 years old are hospitalized with bronchiolitis.
Adenoviruses
Adenoviruses target mucous membranes. They cause about 5 to 10 percent of respiratory tract infections in children and 1 to 7 percent in adults.
Influenza viruses
These viruses cause inflammation in the lungs, nose, and throat. Influenza affects both adults and children. It’s especially dangerous for babies who don’t have strong immune systems.
Causes of bronchiolitis obliterans
This rare condition sometimes occurs for no known reason. Severe cases can lead to death if they’re left untreated. A few causes have been identified and include:
- complication from lung or stem cell transplant
- fumes from e-cigarette smoke
- fumes from chemicals like ammonia, bleach, and chlorine
- respiratory infections
- adverse reactions to medications
Who is at risk for bronchiolitis?
Viral bronchiolitis most commonly affects children under 2 years old. A few risk factors for viral bronchiolitis in babies and young children are:
- not being breastfed
- being born prematurely or born with a heart or lung condition
- having a suppressed immune system
- being exposed to cigarette smoke
- being in crowded places where the virus is present, like daycare centers
Common risk factors for bronchiolitis obliterans in adults are:
- working conditions that expose you to dangerous chemicals
- having had a heart, lung, or bone marrow transplant
- smoking tobacco containing nicotine
- having an autoimmune connective tissue disease
How is bronchiolitis diagnosed?
There are several ways to diagnose both types of bronchiolitis:
- physical exam and medical history evaluation, including potential environmental exposures
- imaging testing, including chest X-rays or a CT scan
- spirometry, which measures how much and how quickly you take in air with each breath
- arterial blood gas tests measure how much oxygen and carbon dioxide are in your blood
Samples of mucus or nasal discharge can help your doctor diagnose the type of virus causing the infection. This testing method is common with babies and small children.
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