Viral Induced Wheeze and Asthma

If you'd like to support us, check out our awesome products:


Wheezing in children is a common clinical presentation in paediatrics. It can be caused by a spectrum of illnesses including bronchiolitis, viral-induced wheeze and asthma.

Wheezing due to viral-induced wheeze or acute viral-induced asthma is caused by narrowing of the airways due to mucus production and bronchoconstriction. Other conditions can present with wheeze, and these are outlined in the differential diagnosis section. 

Want discounted access to all Geeky Medics products, including our medicine flashcard collection? Check out our bundles to save money and supercharge your learning 🔥


Common precipitants of viral-induced wheeze and viral exacerbation of asthma include RSV, rhinovirus, coronaviruses, parainfluenza, influenza and human metapneumoviruses. 

Viral induced wheeze vs asthma

The question often arises ‘is this asthma or viral-induced wheeze?’.

Approximately 50% of children have had at least one episode of wheezing in early childhood, however, most of these are wheeze-free by age six.1

This is due to a combination of increased exposure to viruses in early childhood and smaller airway anatomy that is more prone to cause wheezing due to Poiseuille’s law (small reduction in airway radius increases resistance to airflow as it is inversely proportional to the fourth power of the radius).

The diagnosis of asthma previously has been deferred until the child was able to perform objective testing (e.g. spirometry), typically from age 5 onwards.

However, there is a recent shift to diagnose asthma earlier in children who have recurrent episodes of wheezing along with atopic history and a pattern of symptoms indicating poor control between acute events.2

Risk factors

Risk factors for acute wheeze with viral infections include:

  • Exposure to cigarette smoke
  • Parental history of asthma
  • Maternal smoking during pregnancy
  • Daycare/nursery/school attendance (due to increased risk of exposure to viruses)

Clinical features


Typical symptoms of a viral-induced wheeze or viral-induced asthma include:

  • Upper respiratory tract infection including cough, coryza, blocked/runny nose, sneezing, sore throat
  • Fever
  • Lethargy and fatigue
  • Poor feeding
  • Wheezing sound
  • Tachypnoea and increased work of breathing
  • Complaints of difficulty breathing or chest tightness

It is important to ask about prior wheezing episodes. If a previously higher level of support was required, there is greater suspicion for risk of deterioration.

Specifically, ask about:

  • Needing admission to hospital vs outpatient therapy
  • Needing intravenous therapy on previous occasions
  • Requiring respiratory support (such as CPAP, intubation)
  • Requiring paediatric intensive care unit treatment
  • Atopic history (including eczema, allergic rhinitis, food allergies)
  • Family history of atopy

Clinical examination

A systematic examination should be performed, with an ABCDE approach.

Typical clinical findings in a viral-induced wheeze or viral-induced asthma include:

  • Tachypnoea
  • Hypoxia
  • Wheezing (typically expiratory wheeze, but maybe heard throughout)
  • Prolonged expiratory phase
  • Reduced air entry
  • Accessory muscle use/retractions (also referred to as increased work of breathing)

Classification of severity

Local guidelines should be followed regarding the classification of severity. The below system is based on a guideline by the Royal Children’s Hospital Melbourne:

  • Mild: alert, slight tachypnoea, expiratory wheeze, minimal work of breathing, speaking in full sentences or long cry, oxygen saturations above 95% and normal heart rate
  • Moderate: alert, slight tachypnoea, wheezing during expiration with or without inspiratory wheeze, mild to moderate work of breathing, oxygen saturations 92-95%, able to speak in phrases or shortened cry and mild to moderate tachycardia
  • Severe and life-threatening: agitated/drowsy/confused, marked tachypnoea, moderate to severe work of breathing, inspiratory and expiratory wheeze with prolonged expiratory phase (though wheeze may be absent in a silent chest if there is little or no air entry), oxygen saturations 90% and below (cyanosis is very concerning), and marked tachycardia (or bradycardia)
  • Impending respiratory failure: may be signalled by cyanosis, reduced respiratory effort (if the patient is tiring), reduced alertness (lethargic or agitated), oxygen saturations less than 90% and respiratory acidosis (rising CO2 on venous/capillary blood gas)

Unlike asthma in adults, recording peak flow does not form a part of the initial acute assessment in children.

Differential diagnosis

Wheeze is a common symptom of viral-induced wheeze and asthma exacerbation but can also reflect alternative underlying diagnoses that must be considered.

Differential diagnoses to consider include:2

  • Anaphylaxis: must be considered, especially if associated with sudden onset wheeze and respiratory distress
  • Foreign body aspiration: history of inhalation or aspiration, non-responsiveness to treatments, radiographic evidence of foreign body or air trapping due to a ball-valve mechanism
  • Other pulmonary disorders: for example, cystic fibrosis, laryngomalacia and tracheomalacia
  • Anatomical abnormalities: congenital or acquired (e.g. mediastinal mass in leukaemia/lymphoma)

Less commonly, cardiac, immune and gastrointestinal disorders may present in similar ways.


Investigations for acute viral-induced wheeze or acute viral-induced asthma should be considered to help distinguish between differential diagnoses if there is a lack of response to therapy, or if there is a concern for an alternative or additional diagnosis.

For example, a chest x-ray would be considered if there are focal signs on auscultation despite treatment, to exclude pneumonia/foreign body.3

In addition, investigations are used in the assessment of severe or life-threatening asthma to aid in the monitoring of the condition.

Arterial blood gasses are not used routinely in children. If required, a venous blood gas or capillary blood gas can provide information regarding acid/base status, CO2 level, lactate and potassium.3

In the case of severe or life-threatening cases, consider a chest x-ray to ensure no additional treatable diagnoses (e.g. pneumonia or pneumothorax).


Management of acute viral induced wheeze and viral exacerbation of asthma is dependent on the severity.

Escalating therapy might be required if a patient who presents as lower severity deteriorates or does not respond to initial therapy, this may require input from a senior clinician.

Local management guidelines should be followed. The management below is based on a guideline by the Royal Children’s Hospital Melbourne:


Management of mild severity includes:

  • Commence a trial of salbutamol via spacer and mask (<6 years old = 6 puffs. >6 years old = 12 puffs)
  • A ‘burst therapy’ may be considered, which involves 3 doses of the above, each 20 minutes apart
  • Frequent reassessment to ensure adequate response and need for further dosages
  • Oral steroids may be considered (prednisolone dosage 1-2mg/kg once daily) for 1-3 days (see note below on steroid use in viral-induced wheeze) depending on history and response to therapy


Management of moderate severity includes:

  • Commence inhaled salbutamol as ‘burst therapy’ via spacer and mask with 3 doses, 20 minutes apart
  • Attempt to stretch doses of salbutamol to a minimum of 3 hourly to consider discharge home
  • Consider adding in ipratropium, either as a single dose (<6 years = 4 puffs. >6 years = 8 puffs) or burst therapy (3 doses 20 minutes apart)
  • Oxygen may be required
  • Oral prednisolone 1-2 mg/kg daily for 1-3 days. If unable to stretch doses of salbutamol, consider escalating therapy (see below)


Management of severe severity includes:

  • Early senior involvement in the case of deterioration
  • Burst salbutamol and ipratropium via spacer or nebuliser. Nebulised salbutamol can be given continuous or 20 minutes apart (as a burst). Ipratropium cannot be given continuously (can only be given as a burst with 3 doses 20 minutes apart)
  • Supplemental oxygen may be required
  • Intravenous rather than oral steroids (intravenous hydrocortisone or methylprednisolone) are given
  • If contemplating giving intravenous magnesium sulphate, aminophylline or salbutamol, a senior should be involved immediately and consider retrieval to a higher-level facility/PICU4
Inhalers vs nebulisers

A 2013 Cochrane review found that metered-dose inhalers (MDI) via spacer performed at least as well as nebulisation.

This applied to mild-moderate wheezing episodes, as severe and life-threatening episodes may still require nebulisers.

The benefit of nebulisers in severe and life-threatening include the ability to deliver oxygen at the same time, the ability to deliver ipratropium with salbutamol and the ability to give back-to-back nebulised salbutamol.5

Discharge and follow up

Decisions around discharge depend on severity and response to therapy administered.

Discharge home may be considered if the patient is clinically stable on 3-hourly salbutamol, clinical signs are within normal limits for age, early follow up plans have been arranged and education has been delivered to parents including an asthma action plan and safety-netting.3

The parents must be comfortable with the discharge plan and feel confident to action this at home.

Admission will be required to the ward for ‘stretching of salbutamol’ if the patient does not meet the above criteria.

Transfer to tertiary care or PICU in cases of severe or life-threatening, requiring IV infusions or respiratory support (such as CPAP or intubation).

Use of steroids

The role of steroids in viral-induced wheeze is debated.

Steroids certainly have a role in acute asthma exacerbation, and there is recent evidence that steroids may decrease the length of hospital stay for younger children with mild-moderate viral-induced wheeze (severe and life-threatening were excluded from the study).

Further research is yet to conclude the role of steroids in community-managed viral-induced wheeze.6


 Complications can occur because of the underlying disease or treatment.

Treatment-related complications include:7

  • Salbutamol: tachycardia and hypokalaemia
  • Steroid use: hypertension, stunted growth, weight gain
  • Invasive ventilation: pneumothorax

Disease-related complications include:8

  • Pneumonia
  • Pneumothorax 
  • Respiratory failure (potentially fatal)

Key points

  • Acute viral-induced wheeze/asthma is a common paediatric presentation, often caused by viruses such as RSV, rhinovirus and influenza/parainfluenza.
  • Many children have at least one episode of wheezing in early childhood which does not recur after the age of six. Risk factors for progressing to a diagnosis of asthma include recurrent wheezing episodes, atopic history and symptoms between acute episodes.
  • Clinical features include symptoms of viral URTI, fever, cough, tachypnoea, increased work of breathing, hypoxia and wheeze on auscultation.
  • Acute viral-induced wheeze/asthma is a clinical diagnosis. Differential diagnoses to consider include anaphylaxis, inhaled foreign body and mediastinal mass.
  • Management is based on severity and includes inhaled salbutamol and ipratropium, intravenous or oral steroids, oxygen and respiratory support. Early escalation and senior involvement for severe and life-threatening cases and for patients with non-response to therapy.


Dr Hemani Sharma

Paediatric fellow


Dr Chris Jefferies


  1. Beigelman, Avraham, and Leonard B Bacharier. Infection-Induced Wheezing in Young Children. The Journal of Allergy and Clinical Immunology, U.S. National Library of Medicine, Feb. 2014, Available from: [LINK]
  2. Oo, Stephen, and Peter Le Souëf. RACGP – The Wheezing Child: an Algorithm. Australian Family Physician, vol. 44, no. 6, 2015, pp. 360–364., Available from: [LINK]
  3. The Royal Children’s Hospital Melbourne. Acute asthma. Dec. 2020. Available from: [LINK]
  4. Cochrane. Interventions for Acute Severe Asthma Attacks in Children: an Overview of Cochrane Reviews. 5 Aug. 2020, Available from: [LINK]
  5. Cates, CJ, et al. Holding Chambers (Spacers) versus Nebulisers for Delivery of Beta-Agonist Relievers in the Treatment of an Asthma Attack. Sept. 2013. Available from: [LINK]
  6. Davis, Tessa. Steroids for Pre-School Wheeze. Don’t Forget The Bubbles, 26 Feb. 2020. Available from: [LINK]
  7. Howell, J., Severe Asthma Exacerbations in Children Younger than 12 Years. 2021. Available from: [LINK]
  8. Sawicki, G., Haver, K,. Asthma Exacerbations in Children Younger than 12 Years. 2021. Available from: [LINK]


Print Friendly, PDF & Email