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This is a case of bronchiolitis, the most common respiratory presentation in children under the age of two years old, peaking between the ages of three and six months. It is usually commonly viral in origin and most often due to RSV. Other viral causative agents include human metapneumovirus (hMPV), adenovirus, rhinovirus, and parainfluenza and influenza viruses
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Respiratory syncytial virus (RSV)
QuestionChoice
Streptococcus pneumonia is a common cause for bacterial pneumonia and should be considered in the differential diagnosis; however, as this child had a preceding coryzal illness and the crackles are widespread, this leans more towards a viral diagnosis such as bronchiolitis. In bacterial pneumonia, crackles are more likely to be localised to one zone
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Streptococcus pneumoniae
QuestionChoice
Pseudomonal pneumonia is not a common pathogen as a cause of pneumonia and should prompt consideration of underlying conditions such as cystic fibrosis or immunodeficiency
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Pseudomonas aeruginosa
QuestionChoice
Group B streptococcal infections are a potentially life-threatening cause of sepsis in neonates. One in four women carry group B streptococci vaginally, which can infect the amniotic fluid before delivery or infect the baby during delivery, causing sepsis, pneumonia, or meningitis. Early-onset infections usually occur in the first seven days of life, and late-onset infections are usually from seven to 90 days of life. Pneumonia is more commonly associated with early-onset infection, as the baby swallows infected amniotic fluid during the delivery. This case vignette is not likely to be due to Group B streptococcus
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Group B streptococcus
QuestionChoice
Parainfluenza virus can be a cause of bronchiolitis but is more commonly implicated in croup. Croup usually affects young children aged between six months and three years, with most cases occurring in one-year-olds and presents with a distinctive barking cough
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Parainfluenza virus
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where's the wheeze?
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# Summary
 
Bronchiolitis is a prevalent chest infection that primarily affects infants aged 1-12 months. This infection is typically caused by the Respiratory Syncytial Virus (RSV) and is characterised by symptoms such as a cough, laboured breathing, wheezing, tachypnoea, intercostal recession, grunting, and nasal flaring. Diagnosis is typically made through clinical presentation and possibly chest X-rays. Management includes prophylactic measures in high-risk patients, supportive care, and oxygen therapy, which may escalate to mechanical ventilation. Ribavirin may be used in severe cases. The key complications of bronchiolitis include bronchiolitis obliterans, also known as popcorn lung, which may result from the overactive cellular repair process. 
 

# Definition
 

Bronchiolitis is a widespread chest infection, predominantly affecting infants aged 1-12 months. This lower respiratory tract disease targets the bronchioles, causing inflammation and congestion.
 

# Epidemiology

Bronchiolitis is very common, affecting around 1 in 3 infants. Bronchiolitis mainly affects children under the age of 1, with approximately 90% of affected children being aged between 1-9 months. It is rare beyond the age of 1 year. 

Bronchiolitis epidemics are typically observed during winter months from October to March. 
 

# Aetiology
 

The majority of bronchiolitis cases (around 80%) are attributable to the Respiratory Syncytial Virus (RSV). The virus infects epithelial cells of bronchioles. This causes inflammation, mucous production and the epithelial cells to slough off, obstructing the airways. This obstruction results in hypoxia and breathlessness. 

Risk factors for developing bronchiolitis include:

- Nursery attendance or having older siblings
- Passive smoking in the household
- Overcrowding 
- Exclusive formula-feeding  

More severe bronchiolitis is seen in infants with the following risk factors:

- Prematurity or low birth weight 
- Age < 12 weeks
- History of mechanical ventilation, chronic lung disease, congenital heart disease or neurological disease
- Immunocompromise
- Congenital defects of the airway
- Down's Syndrome 
 

# Signs and Symptoms
 

A diagnosis of bronchiolitis should be considered in an infant with the following:
 
- Preceding coryzal symptoms for 1-3 days 
- Cough
- Either tachypnoea or chest recession 
- Either wheeze or crackles on auscultation

Other symptoms they may present with:

- Fever (typically < 39C) 
- Reduced oral intake 
- Apnoea 


# Differential Diagnosis
 

The differential diagnoses for bronchiolitis primarily include the following:
 

 -  **Asthma**: Characterised by recurrent episodes of wheezing, breathlessness, chest tightness, and coughing, particularly at night or in the early morning. This is typically seen in older children than those affected by bronchiolitis. 
 -  **Pneumonia**: Symptoms include cough with phlegm or pus, high fever (>39C) and persistently focal crackles. 
 -  **Viral Induced Wheeze**: Seen in children with persistent wheeze and a family history of atopy, more commonly seen in children over the age of 1. 
 -  **Foreign body aspiration**: This condition may present with sudden onset of respiratory distress, choking, gagging, wheezing, or coughing.
 

# Investigations
 

Diagnosis of bronchiolitis is primarily clinical based on the characteristic symptoms. 

Further investigations may include:

- Pulse oximetry to monitor oxygen saturation
- Throat swab for respiratory viruses 
- Chest X-rays if focal chest signs or deterioration is seen 
 

# Management
 
The majority of patients can be managed at home, but admission may be indicated for children with:
 
 - Tachypnoea (>60 breaths/min)
 - Reduced oral intake (< 50% normal) 
 - Clinical dehydration
 - Oxygen saturation less than 92% 
 - Cyanosis 
 - Apnoea 
 - Respiratory distress (grunting, intercostal or subcostal recession, tracheal tugging) 


Management of bronchiolitis involves:
 
-  Supportive Care:
     -  Adequate hydration and nutrition
             -  If not tolerating oral intake, an NG tube can be used to provide fluids. 
     -  If fever is causing distress to the infant, paracetamol may be used. 
-  Oxygen Therapy: 
     -  For oxygen saturations less than 90% for children over 6 weeks.
     -  This may be escalated to CPAP in severe cases with threatened respiratory failure.
-  Antiviral Therapy: Ribavirin may be used in severe cases.

Antibiotics, steroids and salbutamol are not used in the management of bronchiolitis. 
 
Prevention may include the administration of Palivizumab (a monoclonal antibody) in high-risk patients (i.e. with haemodynamically significant congenital heart disease). This reduces the risk of RSV-related hospital and PICU admission.

# Complications

Bronchiolitis may result in the following complications:

- Respiratory failure requiring intubation 
- Dehydration 
- Cough lasting weeks following bronchiolitis 
- Bronchiolitis obliterans 
 

Bronchiolitis obliterans:

- A rare, chronic complication of bronchiolitis, colloquially known as popcorn lung. 
- The bronchioles are injured due to infection (usually adenovirus) or inhalation of a harmful substance, leading to an overactive cellular repair process and subsequent build-up of scar tissue. The scar tissue obstructs the bronchioles, impairing oxygen absorption in the body. The scarring and narrowing of the bronchioles may continue to worsen over time, potentially leading to respiratory failure. 
- Lung transplant recipients are at particular risk of developing bronchiolitis obliterans syndrome, with about 50% developing the condition within five years of transplant due to organ rejection.


# Prognosis 

Fortunately for many infants, bronchiolitis can be managed at home and the illness lasts for up to 7 days. The cough may take up to 3 weeks to resolve. 

2-3% of infants, however, require hospitalisation. Risk factors for more severe bronchiolitis include chronic lung disease, immunodeficiency, age under 3 months, prematurity, congenital heart disease and neuromuscular disorders. In these high-risk infants, the mortality rate is roughly 3%. 

# NICE Guidelines 

[NICE Guidelines on Bronchiolitis](https://www.nice.org.uk/guidance/ng9) 
 

# References

[NHS Information on Bronchiolitis](https://www.nhs.uk/conditions/bronchiolitis/) 

[Great Ormond Street Hospital Bronchiolitis Information](https://media.gosh.nhs.uk/documents/Bronchiolitis_F1533_A5_col_FINAL_Mar16.pdf)

[Patient Info Bronchiolitis](https://patient.info/doctor/bronchiolitis-pro)
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Respiratory syncytial virus (RSV) is the most common cause of bronchiolitis in infants, particularly those under six months old.
A five-month-old baby is brought to the Emergency Department with laboured breathing and a raised temperature following a short coryzal illness. On examination, he has subcostal recession and audible, widespread crackles on chest auscultation.

What is the likely causative organism for this presentation?
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