Summary of "Respiratory Syncytial Virus and Bronchiolitis causes, symptoms, diagnosis, treatment, pathology"

Summary of Video: Respiratory Syncytial Virus and Bronchiolitis – Causes, Symptoms, Diagnosis, Treatment, Pathology

Definition of Bronchiolitis

Bronchiolitis is inflammation of the small airways (bronchioles) in the lungs. The term derives from “branchial” (small airways) and “-itis” (inflammation).

Cause

The most common cause of bronchiolitis is infection with Respiratory Syncytial Virus (RSV). Other viral causes include:

Adenovirus
Human bocavirus
Human metapneumovirus

Bacterial causes such as Mycoplasma pneumoniae can also be involved. Sometimes co-infections occur.

RSV Characteristics and Transmission

RSV is an enveloped virus with a negative-sense RNA genome.
It causes infected respiratory epithelial cells to fuse into large multinucleated cells called syncytia (hence the name).
Transmission occurs via respiratory droplets (from sneezing or coughing) within about 2 meters (6 feet) and via contaminated surfaces (fomites).
The virus infects the epithelial lining starting at the nasopharynx and travels down to the bronchioles.

Pathophysiology

RSV hijacks host cells to produce viral proteins, turning them into virus factories.
Infected cells are destroyed, attracting immune cells like natural killer cells.
The immune response causes inflammation, increased mucus secretion, and leaky blood vessels, leading to swelling and thickening of airway walls.
Narrowed airways and mucus plugs cause airflow obstruction.
Mucus plugs can cause atelectasis (collapse of small airways) and air trapping (one-way valve effect), both reducing lung function.
These effects are more severe in children due to their naturally narrower airways.

Symptoms

Early symptoms resemble a common cold: congestion, sore throat, cough.
Severe infection leads to wheezing, difficulty breathing, fever, and hypoxia (low blood oxygen).
Hypoxia can cause increased heart rate and respiratory rate as compensatory mechanisms, but prolonged hypoxia may cause exhaustion and require hospitalization.
Young infants may experience central apnea (temporary cessation of breathing).

Diagnosis

Primarily clinical, based on symptoms, age, and seasonal RSV prevalence.
Risk factors include prematurity, lack of breastfeeding, and neuromuscular disorders.
RSV antigen testing via nasopharyngeal swab can confirm diagnosis but is not always necessary.

Treatment

No specific antiviral therapy exists for bronchiolitis.
Supportive care includes supplemental oxygen and hydration to prevent dehydration.
High-risk children (e.g., premature infants, those with pulmonary or congenital heart disease) may receive monthly prophylactic injections of palivizumab (a monoclonal antibody against RSV).

Summary Recap

Bronchiolitis is inflammation of the small airways mainly affecting infants and young children. The disease results in airway obstruction due to inflammation, mucus plugs, atelectasis, and air trapping, causing breathing difficulties and hypoxia. Diagnosis is clinical, and treatment is supportive.

Key Points in Bullet Format

Bronchiolitis Definition: Inflammation of small airways (bronchioles).
RSV Virus:
- Enveloped, negative-sense RNA virus.
- Causes syncytia formation in respiratory epithelium.
- Transmitted by droplets and fomites.
Infection Pathway: Virus enters nasopharynx → travels down respiratory tree → targets bronchioles.
Pathological Effects:
- Viral replication kills epithelial cells.
- Immune response causes inflammation and mucus secretion.
- Thickened airway walls narrow airways.
- Mucus plugs cause atelectasis and air trapping.
- Reduced oxygen exchange leads to hypoxemia.
Symptoms Progression:
- Mild: Cold-like symptoms.
- Severe: Wheezing, difficulty breathing, fever, hypoxia, apnea.
Diagnosis:
- Clinical based on symptoms, age, and seasonality.
- Nasopharyngeal swab for RSV antigen if needed.
- Consider risk factors (prematurity, breastfeeding status, neuromuscular disorders).
Treatment:
- Supportive: Oxygen supplementation and hydration.
- Prophylaxis: Palivizumab for high-risk infants.