MRCEM Notes

Respiratory Syncytial Virus (RSV)

Microbiology
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Respiratory Syncytial Virus (RSV) is an enveloped RNA virus and common respiratory pathogen that predominantly affects infants and young children. In the UK RSV epidemics start in October and last for 4 to 5 months, peaking in December with little variability in timing from year to year.

Epidemiology

RSV is a leading cause of lower respiratory tract infections in children under 3, with nearly all children experiencing at least one RSV infection by two years of age. Infants, especially those under six months, are at higher risk for severe disease due to their smaller airways and immature immune systems.

RSV is the most common cause of bronchiolitis in infants. Over 60% of children have been infected by their first birthday, and over 80% by 2 years of age

Transmission

Transmission is via respiratory droplets which inoculate the conjunctival or nasopharyngeal mucosa. RSV particles can survive on surfaces for around 6 hours facilitating indirect transmission via contaminated hands or objects.

The incubation period is usually 3-5 days (range 2-8 days), and individuals remain infectious for three to eight days.

Clinical Features

RSV infections can present as mild upper respiratory symptoms, such as rhinorrhea and cough, or progress to severe lower respiratory tract diseases like bronchiolitis and pneumonia. Symptoms may include fever, wheezing, and respiratory distress. In infants, decreased oral intake and lethargy are concerning signs.

Diagnosis

Diagnosis is typically clinical.

Nasopharyngeal aspirate may be tested using reverse transcriptase PCR or rapid antigen detection

Medical Management

Treatment is primarily supportive, focusing on maintaining adequate hydration and oxygenation, with humidified oxygen and fluid/feeding support. Hospitalisation may be necessary for infants with severe respiratory distress or hypoxia.

NICE advise giving oxygen supplementation to babies and children with bronchiolitis if their oxygen saturation is:
  • Persistently < 90%, for children aged 6 weeks and over
  • Persistently < 92%, for babies under 6 weeks or children of any age with underlying health conditions

CPAP should be considered for babies and children with bronchiolitis who have impending respiratory failure.

Role of ribavirin and palivizumab

Ribavirin is licensed for administration by inhalation for the treatment of severe bronchiolitis caused by the RSV in infants, especially when they have other serious diseases. However, there is no evidence that ribavirin produces clinically relevant benefit in RSV bronchiolitis.

Palivizumab is a monoclonal antibody licensed for preventing serious lower respiratory-tract disease caused by respiratory syncytial virus in children at high risk of the disease; it should be prescribed under specialist supervision and on the basis of the likelihood of hospitalisation.

Palivizumab is recommended for:
  • Children < 9 months of age with chronic lung disease (defined as requiring oxygen for at least 28 days from birth) and who were born preterm;
  • Children under 6 months of age with haemodynamically significant, acyanotic congenital heart disease who were born preterm.
Palivizumab should be considered for:
  • Children under 2 years of age with severe combined immunodeficiency syndrome
  • Children under 1 year of age who require long-term ventilation;
  • Children 1–2 years of age who require long-term ventilation and have an additional co-morbidity (including cardiac disease or pulmonary hypertension).

Key Points

  • RSV infection primarily seen in preschool children i.e. under 3 age group.
  • Incubation period is typically 3-5 days (range 2-8 days)
  • RSV is primarily an URTI but the lower respiratory tract is involved in 40% of patients giving rise to bronchiolitis in children.
  • Treatment is usually conservative though 3% of children in the UK are admitted for supportive treatment.
  • Ribavirin can be used but is normally reserved for the severely unwell.
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