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Acute Bronchiolitis


Bronchiolitis is an acute infectious disease of the lower respiratory tract that occurs primarily in the very young, most commonly infants between 2 and 6 months old. It is a clinical diagnosis based upon:

  • Breathing difficulties
  • Cough
  • Decreased feeding
  • Irritability
  • Apnoea in the very young
  • Wheeze or crepitation on auscultation

It is an annual and major cause of morbidity in infancy. Acute bronchiolitis is a very common and may cause serious respiratory illness in children.

It is usually due to a viral infection of the bronchioles. Respiratory syncytial virus (RSV) is the most common pathogen, found in 50-90% of cases. A combination of increased mucus production, cell debris and oedema lead to narrowing and obstruction of small airways.


  • Respiratory syncytial virus (RSV)
  • Human metapneumovirus (hMPV) – causes similar spectrum of illness to RSV and is thought to be the second most common cause
  • Adenovirus – occasionally causes a similar syndrome with a more virulent course
  • Parainfluenza virus
  • Other less common causes include:
    • Mycoplasma pneumoniae
    • Enterovirus
    • Influenza virus
    • Rhinovirus
    • Chlamydophila pneumoniae


  • Peak incidence of respiratory syncytial virus (RSV) infections is in the winter months (November to March), but in Malaysia, it occurs throughout the year.
  • Prevalence may be higher in urban areas.
  • Although it is endemic throughout the year in Malaysia, cyclical periodicity with annual peaks occur, in the months of November, December and January.
  • By their first birthday over 60% of children have been infected and, by two years of age, over 80%. The antibodies that develop following early childhood infection do not prevent further RSV infections throughout life.
  • 3% of infants are admitted to hospital with bronchiolitis. Rates of hospitalisation for bronchiolitis have been rising: the cause is thought to be multifactorial, but includes improved survival of premature infants.

Risk Factors 

Risk factors for acute viral bronchiolitis in children

  • Male sex
  • Age < 6 months
  • Birth during the first half of the RSV season
  • Overcrowding/older siblings
  • Day care exposure
  • Low maternal education (low socioeconomic status)
  • Lack of breast feeding
  • Malnutrition
  • Passive smoke, particularly maternal
  • High altitude

Pre-existing medical conditions in children that increase the risk of acute viral bronchiolitis

  • Prematurity
  • Low birth weight
  • Congenital lung abnormality
  • Chronic lung disease (e.g.cystic fibrosis, bronchopulmonary dysplasia)
  • Congenital heart disease with left to right shunt
  • Immunodeficiency
  • Neurological disease with hypotonia and pharyngeal dis-coordination

Classification of Severity

Mild Disease
  • Alert, active, feeding well
  • None to minimal breathing distress
  • Breathing rate normal to mildly moderately raised (50-70)
Moderate Disease
  • Alert, consoles, feeding decreased
  • Minimal to moderate difficulty in breathing
  • Breathing rate is mildly to moderately raised (50-70)
Severe Disease
  • Fussy, difficult to console, poor feeding
  • Moderate to severe breathing difficulty
  • Breathing rate is moderately to -markedly raised (greater than 70)

Signs & Symptoms

Bronchiolitis usually develops following one to three days of common cold symptoms, including the following:

  • Nasal congestion and discharge.
  • A mild cough.
  • Fever (temperature higher than 100.4ºF or 38ºC). Fever >39°C is unusual and should prompt a thorough examination and further investigations to exclude other possible causes.
  • Decreased appetite.

For the 40% of infants and young children in whom the infection progresses and the lower airways are affected, other symptoms may develop; including the following within 1-2 days (older children and many infants do not usually progress to any further symptoms):

  • Breathing rapidly (60 to 80 times per minute) or with mild to severe difficulty
  • Wheezing, which usually lasts about seven days
  • Persistent coughing (could be paroxysmal), which may last for 14 or more days (persistent cough may also may be due to other serious illnesses that require medical attention)
  • Difficulty in feeding related to nasal congestion and rapid breathing, which can result in dehydration
  • Vomiting
  • Irritability
  • Apnoea (a pause in breathing for more than 15 or 20 seconds) can be the first sign of bronchiolitis in an infant. This occurs more commonly in infants born prematurely and infants who are younger than 2 months.

Signs of severe bronchiolitis include retractions (sucking in of the skin around the ribs and the base of the throat), nasal flaring (when the nostrils enlarge during breathing), and grunting. The effort required to breathe faster and harder is tiring. In severe cases, a child may not be able to continue to breathe on his or her own.

Low oxygen levels (called hypoxia) and blue-tinged skin (called ‘cyanosis) can develop as the illness progresses.

Cyanosis may first be noticed in the finger and toenails; ear lobes; tip of the nose, lips, or tongue; and inside of the cheek. Any of these signs or symptoms requires immediate medical attention.

A child, who is grunting, appears to be tiring, stops breathing, or has cyanosis needs urgent medical attention.


The most common cause of bronchiolitis, respiratory syncytial virus (RSV), is transmitted through droplets that contain viral particles; these are exhaled into the air by breathing, coughing, or sneezing. These droplets can be carried on the hands, where they survive and can spread infection for several hours. If someone with RSV on his or her hands touches a child’s eye, nose, or mouth, the virus can infect the child. Adults infected with RSV can easily transmit the virus to the child.

A child with bronchiolitis should be kept away from other infants and individuals susceptible to severe respiratory infection (e.g., those with chronic heart or lung diseases, those with a weakened immune system) until the wheezing and fever are gone.


Complications of severe bronchiolitis may include:

  • Increasingly labored breathing
  • Cyanosis, a condition in which the skin appears blue or ashen, especially around the lips, caused by lack of oxygen
  • Dehydration
  • Fatigue
  • Severe respiratory failure
  • Apnoea

If these occur, your child may need hospitalisation. Severe respiratory failure may require insertion of a tube into the trachea (intubation) to assist the child’s breathing until the infection is brought under control.

If your infant was born prematurely, has a heart or lung condition, or has a compromised immune system, watch closely for early signs of bronchiolitis. The infection may rapidly become severe, and signs and symptoms of the underlying condition may become worse. In such cases, your child will usually need hospitalisation to monitor his or her health and provide any necessary care.

Infrequently, bronchiolitis is accompanied by another lung infection such as bacterial pneumonia, which is treated separately. Reinfections with RSV after the initial episode may occur but typically aren’t as severe. Repeated episodes of bronchiolitis may precede the development of asthma later in life, but the relationship between the two conditions is unclear.



Primary care

  • Most infants with acute bronchiolitis will have mild, self-limiting illness and can be managed at home. Supportive measures are the mainstay of treatment, with attention toadequate fluid intake, nutrition and temperature control.
  • Within General Practice, a doctor’s role is to assess current severity of illness and, for those with mild-to-moderate disease, to support and monitor. Consider whether the presentation is in the early stages of disease, when a child is more likely to get worse before improving. Teaching parents to spot deterioration is important and when to seek medical review should this occur.
  • For the majority, bronchiolitis lasts for 7-10 days, with 50% well by 2 weeks and only a small subgroup still having some symptoms at 4 weeks. 

Home Treatment

The best treatment for most kids is time to recover and plenty of fluids. Making sure a child drinks enough fluids can be a tricky task, however, because infants with bronchiolitis may not feel like drinking. They should be offered fluids in small amounts at more frequent intervals than usual.

To clear nasal congestion, try a bulb syringe and saline (saltwater) nose drops. This can be especially helpful just before feeding and sleeping. Sometimes, keeping the child in a slight upright position may help improve laboured breathing. Paracetamol can be given to reduce fever and make the child more comfortable. Be sure to follow appropriate dosing and interval of medication based on your child’s weight.

When to refer

Hospital referral is suggested where there is:

  • Poor feeding (<50% usual intake over previous 24 hours) which is inadequate to maintain hydration
  • Lethargy
  • History of apnoea
  • Respiratory rate >60 breaths/minute
  • Nasal flaring or grunting
  • Severe chest wall retractions
  • Cyanosis
  • Saturations ?94%
  • Uncertainty regarding diagnosis
  • Where home care or rapid review cannot be assured

The threshold for admission should be lower in those with significant comorbidities, premature infants and those under 3 months old.

Secondary care

  • Even amongst hospitalised children, supportive care is the mainstay of treatment, including oxygen and intravenous fluids where necessary.
  • Pharmacotherapy:
    • Bronchodilators – modest short-term improvement in clinical scores but no reduction in the rate or duration of hospitalisation.
    • Corticosteroids – trials have consistently failed to provide evidence of benefit.
    •  The use of Hypertonic (3%) saline solution via nebulizer has been shown to increase mucus clearance and significantly reduce hospital stay among non-severe acute bronchiolitis. It improves clinical severity score in both outpatients and inpatients populations.
    • Antibiotics – no evidence to support their routine use. Avoid unless there is a strong suspicion or confirmation of a coexisting bacterial infection
  • Chest physiotherapy is not recommended in infants hospitalised with acute bronchiolitis who are not admitted into intensive care unit.


There are several ways to prevent severe bronchiolitis:

  • Avoid smoking in the child’s home because this increases the risk of respiratory illness.
  • Wash hands frequently with soap and water, especially before touching an infant.
  • Avoid contact with other adults and children with upper respiratory infection. It may be difficult or impossible to completely avoid persons who are ill, although parents can try to limit direct contact. In addition, infants or children who are sick should not be sent to day care or school because this can potentially cause others to become ill.
  • A yearly vaccination for influenza virus is recommended for everyone older than 6 months, especially for household contacts of children younger than five years, and out of home caregivers of children younger than five years.
  • Infants who are younger than 24 months with specific types of chronic lung disease or heart disease, as well as infants who are born preterm (between 29 and 35 weeks gestation) if deemed appropriate by the managing doctor may be given a special medication (palivizumab) to prevent severe respiratory syncytial virus (RSV) infection requiring hospitalis Palivizumab is a monoclonal antibody that protects the lungs from severe infection from RSV. It is given as an injection into the muscle once per month for five months starting before RSV season. There is low risk of serious side effects with palivizumab. However it is very costly.
Last Reviewed :  27 June 2016
Writer : Dr. Noor Hafiza bt. Nordin
Accreditor : Dr. Norzila bt. Mohamed Zainuddin