OVERVIEW

What is bronchiolitis?

Bronchiolitis is a relatively common lower respiratory tract infection in infants and young children.

What causes bronchiolitis?

It is mostly caused by viral infections.

What are the symptoms of bronchiolitis?

It often presents with rapid, shallow breathing and wheezing.

Who is most likely to get bronchiolitis? Why?

Bronchiolitis is most common in children under 2 years old, especially infants aged 1–6 months.

This is because infants' immune systems are not yet fully developed, making them less resistant to many pathogens in the environment.

How should bronchiolitis be treated?

If the baby's breathing difficulty is mild, outpatient care and home observation are sufficient. If symptoms like wheezing are severe, hospitalization may be required.

What is the mortality rate of bronchiolitis? What are the causes of death?

The mortality rate is 1%, with severe cases often dying from respiratory failure or severe acidosis.

What are bronchioles?

The human lower respiratory tract consists of the trachea, bronchioles, and alveoli. The bronchioles branch progressively finer toward the alveoli, with those measuring 75–300 μm in diameter called bronchioles.

What complications can bronchiolitis cause?

When bronchioles are affected, they can easily become blocked, leading to breathing difficulties.

SYMPTOMS

What are the manifestations of bronchiolitis?

The main manifestations are paroxysmal coughing and difficulty breathing. Difficulty breathing often presents as rapid, shallow breathing, wheezing, and breathlessness, particularly characterized by labored exhalation and significantly prolonged expiration time.

Some children may exhibit short, "whooshing" wheezing sounds during exhalation, or noticeable nasal flaring and retractions (visible inward pulling of the neck and chest, as well as the spaces between the ribs) during breathing.

Do all children with bronchiolitis have a high fever?

No.

Some children may have a high fever, while others may experience moderate fever, low-grade fever, or no fever at all.

What signs indicate severe bronchiolitis?

In severe cases, children may show significant difficulty breathing, wheezing, retractions, poor responsiveness, pale or bluish skin, reduced feeding, markedly decreased urine output, and a rapid heart rate. These signs often indicate a serious condition.

It's important to note that the severity of the illness is not necessarily linked to the child's temperature but rather to the degree of respiratory distress.

What is the difference between bronchiolitis and pneumonia?

The distinction between bronchiolitis and pneumonia remains debated in academia. Many experts in China consider bronchiolitis a specific type of pneumonia, though this view is still contested among doctors and lacks a definitive conclusion. However, these debates do not affect treatment approaches.

What dangers can bronchiolitis cause?

The disease significantly impacts a child's breathing. Severe cases may lead to pronounced respiratory distress, respiratory failure, hypoxia, and carbon dioxide retention, which can be life-threatening.

Can bronchiolitis recur?

Yes.

Immunity to viruses like respiratory syncytial virus (RSV) is short-lived, making reinfection possible, especially in children with an allergic predisposition, who are more prone to repeated infections.

How soon after bronchiolitis can recurrent asthma develop in infants?

After bronchiolitis, infants are prone to recurrent wheezing within six months. About half of these children may develop asthma within the next 2 to 7 years.

CAUSES

How does bronchiolitis occur?

Most cases are caused by viral infections, with respiratory syncytial virus (RSV) being the most common. Other viruses such as influenza virus, parainfluenza virus, and adenovirus can also cause it.

Viral infections can trigger inflammation in the bronchioles. The tiny lumens are highly prone to obstruction due to sticky secretions, edema, and muscle contraction, potentially leading to emphysema or atelectasis (lack of air or reduced air in the lungs, weakening normal ventilation). As a result, bronchiolitis often causes more pronounced breathing difficulties compared to typical bronchitis.

Why are babies more susceptible to bronchiolitis?

Infants and young children have underdeveloped immune systems, making them vulnerable to many pathogens in the environment. Exposure to infections, especially when family members have respiratory infections, increases their risk.

Children under two have narrower airways. During infections, mucosal swelling and increased secretions can easily block these small passages, leading to noticeable breathing difficulties.

At what age is bronchiolitis most common?

Bronchiolitis primarily affects infants under 2 years old, with 80% of cases occurring in babies under 1 year, particularly those aged 1–6 months.

Is bronchiolitis contagious? How does it spread?

Yes.

Since the disease is mostly viral, coughing can spread the virus through saliva droplets.

Who is most vulnerable to bronchiolitis infection? Why?

Infants and young children generally lack immunity to viruses like RSV and influenza, making them highly susceptible.

Older children and adults, however, have stronger immune systems and are less likely to be infected. Even if infected, symptoms are usually mild, often limited to upper respiratory infections.

DIAGNOSIS

What tests are needed to diagnose bronchiolitis?

• Chest X-ray: To assess lung condition and rule out other types of pneumonia. Findings may include emphysema and thickened lung markings.
• Pathogen testing: Throat swabs, sputum culture, or blood culture may be performed to identify specific pathogens.
• Blood tests: To determine bacterial infection or complications.

How is bronchiolitis different from general acute bronchitis?

Bronchiolitis presents with clinical symptoms more similar to pneumonia, is more severe than typical acute bronchitis, and often exhibits more pronounced wheezing and breathing difficulties.

What is the relationship between bronchiolitis and childhood asthma?

Most first episodes of infectious wheezing in infants are caused by bronchiolitis. If recurrent episodes exceed 3 times and there is a family history of allergies, 22.1% to 53.2% of cases may potentially develop into asthma.

TREATMENT

Which department should I visit for bronchiolitis?

The most appropriate department is pediatric respiratory medicine. If the hospital does not have this department, you can also visit pediatric internal medicine or the respiratory medicine department.

Does bronchiolitis require hospitalization?

It depends.

If the baby's breathing difficulties are mild, outpatient treatment and close monitoring at home may suffice. However, babies with severe breathing difficulties, especially those experiencing respiratory failure, must be hospitalized.

How is bronchiolitis treated?

Treatment is primarily symptomatic and supportive, including:

• Nebulization: Inhalation therapy to moisten and loosen phlegm, making it easier to expel secretions from the bronchi, combined with back patting to relieve wheezing.
• Oxygen and respiratory support: Babies showing signs of hypoxia (restlessness, cyanosis, or low blood oxygen saturation) may require oxygen therapy. Severe cases with respiratory failure may need oxygen or ventilator support.
• Anti-infective therapy: Targeted treatment can be used after identifying the specific pathogen. However, most viral infections have no specific antiviral drugs, and recovery relies on the body's natural healing.
• Hydration: Due to rapid breathing or fever, babies may lose more fluids than usual. Doctors may provide oral or intravenous fluids to prevent dehydration.
• Corticosteroid therapy: Used to reduce inflammation and control wheezing when necessary.

Are antiviral drugs needed for bronchiolitis treatment?

Since viral infections are often self-limiting (resolving on their own over time), antiviral drugs are usually unnecessary.

Are antibiotics needed for bronchiolitis?

It depends.

Most cases are caused by viruses, so antibiotics are generally not required. However, if there is evidence of bacterial co-infection, antibiotics may be used.

Why might sedation be needed for bronchiolitis patients?

Severely affected babies often have significant breathing difficulties and reduced lung function. Crying increases oxygen demand and the risk of respiratory failure, so sedation may be necessary in some cases.

When is corticosteroid therapy used for bronchiolitis?

Corticosteroids may be used if wheezing and breathing difficulties remain severe despite nebulization and other treatments, helping to relieve respiratory distress.

Do corticosteroids have significant side effects for bronchiolitis patients?

No.

The doses used for bronchiolitis are minimal and short-term, stopping once symptoms improve. This makes them safe with no impact on growth or health. Even long-term use for conditions like asthma is generally beneficial when managed properly.

Is intravenous (IV) therapy necessary for bronchiolitis?

Mild cases may not require IV fluids. However, severe cases with poor feeding, lethargy, or significant breathing difficulties may need IV treatment.

How long does bronchiolitis take to recover?

Mild cases typically resolve in 5–15 days (average 10 days). Severe cases may take longer, with about 1% of infants dying due to complications.

Can bronchiolitis be completely cured?

Most babies recover fully.

However, those with pre-existing heart/lung conditions, malnutrition, immunodeficiency, or prematurity face higher mortality risks due to prolonged wheezing, apnea, respiratory failure, or severe dehydration.

Must bronchiolitis patients fully recover before discharge?

No.

Since treatment is symptom-based, babies can be discharged once breathing improves and feeding/alertness returns, continuing recovery at home.

DIET & LIFESTYLE

What should be noted when caring for children with bronchiolitis?

• Encourage drinking more water or milk appropriately to reduce the viscosity of phlegm.
• Feed smaller amounts each time but more frequently to minimize choking.
• Pat the back frequently to help expel phlegm from the trachea.

PREVENTION

How to prevent bronchiolitis?

• Wash hands frequently with soap or hand sanitizer.
• Keep living spaces well-ventilated to reduce the risk of pathogen exposure for babies.
• Practice pathogen isolation—family members with "colds" or other respiratory infections should stay away from babies or wear masks to minimize cross-infection.
• Get vaccinated on schedule, such as receiving the annual flu vaccine.