Respiratory Syncytial Virus
from https://www.ncbi.nlm.nih.gov/books/NBK459215/
- RSV: common virus infecting children and adults, especially the elderly.
- Common clinical presentation: upper respiratory infection, bronchiolitis in children.
- Severe cases: pneumonia, respiratory failure, apnea, death.
- Mainstay of treatment: supportive care.
- Passive immunization: available for at-risk children.
- Antiviral treatment: limited by efficacy, side effects, and cost.
- Interprofessional team: essential for management, care coordination, and improved outcomes.
Introduction
- RSV: widespread virus infecting children and elderly.
- Commonly presents: as upper respiratory infection; in young children, often causes bronchiolitis.
- Severe cases: can lead to pneumonia, respiratory failure, apnea, and death.
- Treatment: mainly supportive; passive preventive immunization available for at-risk children.
- Antiviral treatment: ribavirin, used on a case-by-case basis due to limited efficacy and high cost.
Etiology
- RSV: single-stranded RNA virus, Paramyxoviridae family, Pneumovirus genus.
- Discovered: in 1955 in chimpanzees, confirmed in humans shortly after.
- Structure: bilipid-layer envelope, ribonucleoprotein core, membrane proteins (attachment and fusion).
- Serotype and strains: one serotype, two strains (A and B) with structural protein variations.
Epidemiology
- Lack of long-term immunity: frequent reinfections.
- Infection rate: 90% of children within first 2 years.
- Lower respiratory tract illness: significant minority of cases, primarily bronchiolitis.
- High-risk groups: premature infants, cardiac, pulmonary, neurologic, immunosuppressive disorders, elderly.
- Global impact: 33 million lower respiratory tract illnesses, 3 million hospitalizations, up to 199,000 childhood deaths annually.
- Seasonal variation: winter-spring in temperate climates, less pronounced in tropical climates.
Pathophysiology
- Transmission: respiratory droplets.
- Incubation period: 2-8 days (mean 4-6 days).
- Target cells: apical ciliated epithelial cells in respiratory tract.
- Viral entry: RSV-G glycoprotein for attachment, RSV-F glycoprotein for fusion.
- Immune response: humoral and cytotoxic T-cell activation.
- Consequences: small airway obstruction, mucus plugging, ciliary dysfunction, airway edema, decreased lung compliance.
Histopathology
- Severe disease findings: abundant respiratory epithelial cell death, airway edema, immune cell infiltration (polymorphonuclear early, lymphomononuclear later).
History and Physical
- Upper respiratory illness: rhinorrhea, nasal congestion, cough, sneezing, fever, myalgia.
- Lower respiratory involvement: rhonchorous breath sounds, tachypnea, accessory muscle use, wheezes, prolonged expiration.
- Severe cases: viral pneumonia, hypoxia, lethargy, apnea, acute respiratory failure.
Evaluation
- Clinical diagnosis: no confirmatory testing required.
- Specific testing: rapid antigen and PCR testing.
- Antigen testing: quick, inexpensive, specific, ~80% sensitivity.
- PCR testing: more sensitive, can detect multiple organisms, higher cost, requires specialized equipment.
- Radiographic findings: hyperinflation, patchy atelectasis, peribronchial thickening.
Treatment / Management
- Supportive care:
- Nasal suction and lubrication.
- Antipyretics for fever.
- Assisted hydration: oral, nasogastric tube, or intravenous.
- Oxygen for hypoxia.
- Ventilatory support: high-flow nasal cannula, CPAP, intubation, mechanical ventilation.
- Immune prophylaxis: palivizumab for at-risk infants.
- Palivizumab: humanized murine monoclonal antibody, monthly administration during RSV season.
- Antiviral medication: ribavirin (case-by-case basis).
- Other treatments: albuterol, racemic epinephrine, steroids, hypertonic saline, antibiotics, chest physical therapy (not recommended).
Differential Diagnosis
- Asthma
- Bronchiolitis
- Influenza
- Croup
- Bronchitis
- Pneumonia
Prognosis
- Excellent outcome: for most children.
- Hospitalization: typically 3-4 days.
- High-risk infants: longer stays, higher rates of mechanical ventilation and ICU admission.
- Mortality: less than 1%, <400 deaths/year in the US.
Deterrence and Patient Education
- Hand washing: critical for prevention.
- Hygiene practices: avoid sharing drinks/utensils, clean surfaces, isolate infected individuals.
Pearls and Other Issues
- Severe RSV infection: increases risk for recurrent wheezing, childhood asthma, allergic sensitization.
- Palivizumab prophylaxis: may decrease incidence of recurrent wheezing.
Outcomes
- Majority of children: excellent outcome.
- High-risk infants: longer admissions, potential need for mechanical ventilation.
- Long-term: possible wheezing, but recent studies show no increased asthma risk
RSV immunisation
https://www.vaccinate.initiatives.qld.gov.au/what-to-vaccinate-against/rsv-immunisation
Medication Used: Nirsevimab (Brand Name: Beyfortus®)
- Type: Long-acting monoclonal antibody
- Protection Duration: At least 5 months
- Effectiveness: Up to 80% in decreasing infant hospitalisations related to RSV
- Approval: Determined safe and effective by Therapeutic Goods Administration (TGA) in November 2023
Program Commencement and Eligible Groups
- Eligibility: Only infants and young children who are residents of Queensland
- Not required to be Medicare eligible
- Availability:
- Queensland Birthing Hospitals (public and private): Starting 15 April 2024 for newborns
- Other Immunisation Providers: Access via special-order process starting 22 April 2024
Program Focus
- Ensuring infants and young children at highest risk of severe RSV are protected due to global supply constraints.
Eligible Groups for RSV Immunisation
- All infants born on or after 1 February 2024
- At birth or prior to discharge from hospital
- Not immunised in hospital: Access nirsevimab up to less than 8 months of age through primary care providers
- Ineligible once they reach 8 months of age
- Aboriginal and Torres Strait Islander infants less than 8 months of age
- Eligible even if born prior to the program commencement, if they receive nirsevimab before reaching 8 months of age
- Ineligible once they reach 8 months of age
- Infants with certain complex medical conditions from birth to less than 8 months of age*
- Eligible if born prior to the program commencement and receive nirsevimab before reaching 8 months of age
- Ineligible once they reach 8 months of age
- Young children with certain complex medical conditions from 8 months to less than 20 months of age, until 31 October 2024*
- Time-limited: Doses available until 31 October 2024
- Ineligible once they reach 20 months of age
- Restricted stock due to the specialised nature of this cohort and supply constraints
Eligible Complex Medical Conditions*
- Prematurity: Born less than 32 weeks gestation and less than 12 months of age
- Chronic Neonatal Lung Disease: Neonates requiring home oxygen/other respiratory support, less than 20 months of age
- Significant Respiratory Conditions: Requiring respiratory support such as tracheostomy, non-invasive ventilation (BIPAP or CPAP), or cystic fibrosis with severe lung disease or weight for length less than 10th percentile, less than 20 months of age
- Congenital Heart Disease: Haemodynamically significant, less than 20 months of age
- Severe Primary Immunodeficiency: Less than 20 months of age and not yet received curative treatment
- Trisomy 21: Less than 20 months of age
- Post Solid-Organ Transplant or End Stage Organ Disease: Awaiting transplant, less than 20 months of age
- Active Chemotherapy: Infants less than 20 months of age
- HSCT: Infants less than 20 months of age within 28 days prior to HSCT or prior to engraftment post HSCT
- Neuromuscular Disorders: Associated with significantly impaired respiratory function such as spinal muscular atrophy (SMA), less than 20 months of age
- Other Infants: Less than 20 months of age by exception only, with complex medical conditions after discussion with a Paediatric Infectious Diseases Specialist
Notes
- Clinical Guidance for Immunisation Service Providers: Refer for infants born to a person who received RSV vaccination during pregnancy.
- Special-order Process: Available for other immunisation providers starting 22 April 2024.