Respiratory Syncytial Virus (RSV)

Morphology

SS negative-sense RNA virus
From the paramyxoviridae family
Enveloped nucleocapsid that encodes for 10 viral proteins
Matrix is made of M and M2 proteins

The viral envelope has two glycoproteins :

G protein:
- By which virus attaches to cell surface
F- protein ( Fusion protein:
- which bring about the fusion between viral and host cell membranes.
- It is also responsible for cell to cell fusion, which leads to the characteristic syncytial formation.

Types

RSV can be subtyped into:

Type A
Type B

Types account for differences in:

The G protein composition
The conservation of the F protein in these 2 subtypes

Transmission:

Direct contact with respiratory droplets such as sneezing or coughing
Close indirect contact with contaminated fomites such as used tissues

Clinical Manifestations:

RSV infection leads to a wide spectrum of respiratory illnesses.

1. In infant cause:

pneumonia
bronchiolitis
tracheobronchitis.
In this age group, illness begins most frequently with rhinorrhea, low-grade fever, often accompanied by a cough and wheezing.

2. In adults, the most common symptoms are:

a common cold, with rhinorrhea
sore throat
cough.
It causes severe pneumonia in elderly.

3. Sinusitis, otitis media, and worsening of chronic obstructive and reactive airway disease are also associated with RSV infection.

Diagnosis

For Bronchiolitis:

Chest X-ray shows:

Hyperinflation

Multiple areas of interstitial infiltration

Bud tree Appearance:

MC cause of tree in bud (bronchiectasis) appearance is Mycobacterium tuberculosis (endobronchial).
Most common specific cause of tree in bud appearance in HSL (bone marrow) transplant patients is:
- CMV (30-70%) > RSV (18%) > M. tuberculosis (5-6%) > Pneumocystis > Invasive aspergillosis.

Treatment

Oxygen: Mainstay of therapy.
Aerosolized ribavirin is used in the treatment of bronchiolitis with RSv

Prevention

Palivizumab:

Humanized monoclonal antibody
Directed against an epitope in the A antigen site on the F surface protein of RSV.
Licensed for the prevention of RSV infection in high-risk infants and children.
Once-monthly intramuscular injections (15 mg/kg) for 5 months beginning at the start of the RSV season

Exam Important

Morphology

SS negative-sense RNA virus
The viral envelope has two glycoproteins :

G protein:
- By which virus attaches to cell surface
F- protein ( Fusion protein:
- which bring about the fusion between viral and host cell membranes.