Respiratory Syncytial Virus Infection

Respiratory syncytial virus infection is a common respiratory illness causing a spectrum from mild upper respiratory symptoms to severe bronchiolitis and pneumonia. The greatest burden of severe disease is in infants under six months, older adults and immunocompromised patients.

Clinical relevance is increasing given the recent availability of specific preventive monoclonal antibodies and vaccines.

Virology

The virus is an enveloped RNA virus of the Pneumoviridae family. It spreads via respiratory droplets and contact with contaminated surfaces, with seasonal winter epidemics in temperate climates. Reinfection throughout life is the norm since natural infection confers only partial and waning immunity.

In infants, presentation ranges from mild coryza to bronchiolitis with wheeze, tachypnoea and feeding difficulty.

In older children and healthy adults, infection typically produces a self limiting upper respiratory illness with rhinorrhoea, cough and mild fever.

In older adults, particularly those with chronic cardiopulmonary disease, and in immunocompromised patients of any age, infection can produce significant lower respiratory tract disease. This includes pneumonia, hypoxia and exacerbation of underlying cardiac or respiratory conditions. The disease burden is increasingly recognised as comparable to influenza in this population.

Polymerase chain reaction testing on a nasopharyngeal swab or aspirate is the most sensitive confirmatory test, with rapid antigen testing available as a faster though less sensitive alternative, particularly useful in infants where viral load is typically higher.

Chest radiography and blood gas analysis are reserved for patients with significant respiratory compromise, following the same principles applied to other causes of pneumonia and bronchiolitis.

Treatment is supportive in the great majority of cases, following the same principles as bronchiolitis in infants and viral pneumonia in adults. Give supplemental oxygen to maintain saturation above 92 to 94 percent, and adequate hydration. Where oral intake is inadequate, give nasogastric or intravenous fluid support.

Ribavirin is a nucleoside analogue with activity against respiratory syncytial virus. It is reserved for severe disease in significantly immunocompromised patients (haematopoietic stem cell transplant recipients, lung transplant recipients).

It is given as inhaled therapy or, in some protocols, orally at 600 mg twice daily, under specialist infectious disease and respiratory guidance. Evidence is limited and cost is significant. Teratogenic risk requires strict contraception precautions for staff and patients of childbearing potential.

Palivizumab 15 mg per kg intramuscularly once monthly through the respiratory syncytial virus season is established prophylaxis for high risk infants (significant prematurity, chronic lung disease of prematurity, haemodynamically significant congenital heart disease).

Nirsevimab is a long acting monoclonal antibody given as a single intramuscular dose (typically 50 mg for infants under 5 kg and 100 mg for infants 5 kg or above) before or during the first respiratory syncytial virus season. It provides broader protection across the general infant population.

Nirsevimab is increasingly replacing palivizumab, given a single dose covers the full season.

Respiratory syncytial virus vaccines (bivalent prefusion F protein vaccines) are approved for adults aged 60 and above and for pregnant women between 32 and 36 weeks gestation (protecting the neonate through transplacental antibody transfer). They are given as a single intramuscular dose.

The choice between maternal vaccination and infant nirsevimab is guided by local programme availability and timing of pregnancy.