INTRODUCTION TO RESPIRATORY SYNCYTIAL VIRUS (RSV)
⇒ The Respiratory syncytial virus is the most important causative agent of bronchiolitis & pneumonitis in infants and causes common cold or rhinitis in older children and adults.
⇒ RSV was first isolated in 1956 from chimpanzees with coryza & was called the chimpanzee coryza agent.
⇒ A year later, the virus was obtained from children with lower respiratory tract infection and found associated with the formation of multinucleated syncytia and was named as Respiratory Syncytial Virus.
⇒ Respiratory Syncytial virus belongs to the pneumovirus genus of Paramyxoviridae family.
MORPHOLOGY OF RESPIRATORY SYNCYTIAL VIRUS (RSV)
⇒ RSV is a Spherical, Enveloped & Pleomorphic virus.
⇒ Size: 150-300 nm in diameter.
⇒ Envelope has two glycoproteins – the G protein (by which virus attaches cell surface) and Fusion (F) protein (brings about the fusion of viral & host cell membrane).
⇒ RSV does not have Hemagglutinin protein or Neuraminidase activity.
⇒ Genetic Material:- Linear ssRNA
RESISTANCE SHOWN BY RESPIRATORY SYNCYTIAL VIRUS (RSV)
⇒ RSV is highly labile and is inactivated rapidly at room temperature
⇒ It can be preserved by lyophilization.
CULTIVATION OF RESPIRATORY SYNCYTIAL VIRUS (RSV)
⇒ RSV does not grow in eggs but can be cultivated on human cell cultures, such as HeLa and HEp-2; it can also be cultivated in monkey kidney.
PATHOGENESIS OF RESPIRATORY SYNCYTIAL VIRUS (RSV)
⇒ RSV is the most important causative agent of the lower respiratory tract in infants causing Tracheobronchitis, Bronchiolitis, and Pneumonia.
The virus is transmitted by close contact, and through
Contaminated fingers and fomites via nose or eye.
⇓
The virus replicates initially in epithelial cells
of Nasopharynx.
⇓
Virus reaches lower respiratory tract and causes
the lymphocyte migration resulting in peribronchiolar infiltration.
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Produces Bronchitis and/or Pneumonia.
CLINICAL FEATURES OF RSV INFECTION
⇒ The incubation period of Respiratory Syncytial Virus is 3-6 days.
⇒ Most of the RSV infections are symptomatic.
⇒ The symptoms of RSV infections in infants include –
- Febrile Rhinorrhea
- Cough
- Wheezing
- Tracheobronchitis
- Bronchiolitis
- Pneumonia
⇒ In young children, RSV causes Otitis Media.
LAB DIAGNOSIS OF RESPIRATORY SYNCYTIAL VIRUS (RSV)
⇒ Specimen: Nasopharyngeal Swabs or Nasal washings
⇒ Isolation of the virus: Samples should be inoculated in cell cultures (HeLa or HEp-2 or monkey kidney). The cytopathic effects take about 5-15 day to appear.
⇒ Serology: Virus-specific antibodies can be detected by ELISA, CFT, Neutralization test or Immunofluorescence tests.
⇒ PCR: RT-PCR technique is sensitive and rapid.
PROPHYLAXIS OF RESPIRATORY SYNCYTIAL VIRUS (RSV) INFECTION
⇒ No effective Vaccine is available at present.
TREATMENT OF RSV INFECTION
⇒ Administration of Ribavirin by continuous aerosol has been found useful in the treatment of RSV associated illness.
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