207.1 ð é«åžçç
207.1.0.1 ð äžé éé»
- Virus: ssRNA, Pneumoviridae family, related to HMPV
- Universal childhood infection (95%+ infected by 2 yr)
- Re-infection lifelong (immunity wanes)
- High-risk groups:
- < 6 months (especially < 3 months) â most severe pediatric
- Preterm infants
- Bronchopulmonary dysplasia / chronic lung disease of prematurity
- Congenital heart disease (hemodynamically significant)
- Immunocompromise
- ⥠65 yr (similar mortality to flu in this age group)
- Chronic cardiopulmonary disease
- Nursing home residents
- Clinical (infants):
- Bronchiolitis (#1 form): wheezing + tachypnea + retractions + fever 1-3 days after URI prodrome
- Apnea (especially preterm < 3 mo)
- Hypoxia + respiratory failure (severe)
- Pneumonia
- Clinical (older child / adult):
- URI / common cold (mild)
- Bronchitis
- Pneumonia (elderly, immunocompromise)
- COPD / asthma exacerbation
- Diagnosis:
- Multiplex respiratory PCR
- Rapid antigen test (sens ~ 70%)
- Not routinely needed in classic bronchiolitis
- Treatment:
- Supportive: oxygen, hydration, suction, mechanical ventilation
- NO routine antiviral (ribavirin limited efficacy, rare use)
- Bronchodilators / steroid generally NOT helpful in bronchiolitis (AAP 2014)
- High-flow nasal cannula + CPAP for moderate-severe
- Mechanical ventilation for severe
- Prevention (2023-2024 game changer):
- Nirsevimab (Beyfortus, FDA 2023) â long-acting mAb against F protein; single dose covers RSV season
- Universal infants entering 1st RSV season (ACIP 2024)
- High-risk children entering 2nd season
- Maternal RSVpreF vaccine (Abrysvo) â Pfizer; 32-36 wk gestation
- Maternal Ab transfer protects newborn †6 mo
- Adult vaccines (2023 FDA approvals):
- Arexvy (GSK) â RSVpreF subunit
- Abrysvo (Pfizer) â RSVpreF subunit
- mRESVIA (Moderna, FDA 2024) â mRNA
- For ⥠60 yr (some 50+) routine; or chronic disease 18+
- Palivizumab (Synagis) â older mAb, monthly during RSV season, high-risk infants only â being replaced
- Nirsevimab (Beyfortus, FDA 2023) â long-acting mAb against F protein; single dose covers RSV season
207.1.0.2 1ïžâ£ Virology
- ssRNA, Pneumoviridae family
- Subgroups A + B (slightly antigenically distinct)
- Surface proteins F (fusion) + G (attachment) primary antigens
- F protein has prefusion + postfusion conformations
- Prefusion F (RSVpreF) is the optimal vaccine + mAb target (Crank, McLellan 2013-)
207.1.0.3 2ïžâ£ Epidemiology
207.1.0.3.1 Seasonality
- N hemisphere: late autumn-early spring (Oct-April peak Dec-Feb)
- S hemisphere: opposite
- Tropical: less seasonal
- 2023-2024 post-COVID resurgence (immunity gap)
207.1.0.4 3ïžâ£ Clinical â Pediatric
207.1.0.4.1 Bronchiolitis (Infant)
- #1 viral LRTI in infants globally
- Peak age 2-6 months
- Onset: 2-3 day URI prodrome â respiratory distress
- Wheezing, tachypnea, retractions, nasal flaring
- Hypoxia + respiratory failure in severe
- Fever low-grade
- Auscultation: wheezes + crackles
- Self-limited 7-10 days
207.1.0.4.2 Apnea (Preterm + < 3 mo)
- Especially preterm infants + < 3 months
- Can be presenting feature
- Monitoring critical (preterm)
207.1.0.4.4 Severe Disease Criteria
- Respiratory rate > 70
- SaO2 < 92% on room air
- Severe retractions / accessory muscle use
- Cyanosis
- Apnea
- Dehydration
- Toxic appearance
207.1.0.5 4ïžâ£ Clinical â Adults
207.1.0.5.2 Elderly + High-Risk
- Pneumonia in elderly
- COPD + asthma exacerbation
- Heart failure exacerbation
- Severe systemic illness
207.1.0.6 5ïžâ£ Diagnosis
207.1.0.6.1 Multiplex Respiratory PCR
- Most sensitive
- 1-2 hr turnaround
- Useful for severe / immunocompromise / outbreak
207.1.0.6.2 Rapid Antigen Test
- POC, 15-30 min
- Sensitivity ~ 70% (lower than flu rapid)
- Useful for outpatient triage
207.1.0.7 6ïžâ£ Treatment
207.1.0.7.1 Supportive Care Core
- Oxygen to maintain SaO2 > 92%
- IV fluids / NG feeds if poor oral intake
- Suction nasopharynx (especially infants)
- High-flow nasal cannula for moderate-severe
- CPAP for severe
- Mechanical ventilation for respiratory failure
- ECMO for refractory ARDS (rare)
207.1.0.7.2 Bronchodilators (Limited Efficacy)
- AAP 2014 guidelines: donât routinely use bronchodilators in bronchiolitis (no clear benefit)
- Trial dose may be considered; continue if obvious response
207.1.0.7.3 Steroids
- Donât routinely use in bronchiolitis (no benefit, AAP)
- COPD / asthma exacerbation: steroid per usual algorithms
207.1.0.7.4 Antibiotics
- Donât routinely use unless secondary bacterial infection suspected
- Common URI / pneumonia bacterial agents if super-infection
207.1.0.8 7ïžâ£ Prevention â 2023-2024 Game Changer
207.1.0.8.1 Nirsevimab (Beyfortus, FDA 2023)
- Long-acting mAb against prefusion F protein
- Half-life ~ 70 days â single dose covers entire RSV season
- Indication: universal infants entering 1st RSV season; high-risk children entering 2nd season (⥠24 mo with high-risk conditions)
- Dose:
- 50 mg IM if < 5 kg
- 100 mg IM if ⥠5 kg
- 2024 ACIP universal recommendation
- 5-fold reduction in RSV hospitalization (MELODY trial)
- Replacing palivizumab in most situations
207.1.0.8.2 Maternal RSVpreF (Abrysvo)
- Pfizer, FDA 2023
- Given at 32-36 wk gestation
- Maternal Ab transferred transplacental â newborn protected †6 mo
- Alternative to nirsevimab (donât typically give both â one or the other)
- MATISSE trial: 70% efficacy reducing infant RSV LRTI
207.1.0.8.3 Palivizumab (Synagis)
- Older mAb, monthly during RSV season (5 doses)
- For high-risk infants only:
- Preterm < 29 wk gestation
- Chronic lung disease of prematurity
- Hemodynamically significant congenital heart disease
- Being replaced by nirsevimab in most institutions
207.1.0.8.4 Adult Vaccines (2023+ FDA Approvals)
207.1.0.8.4.1 Arexvy (GSK)
- Recombinant prefusion F protein + AS01E adjuvant
- ⥠60 yr (initially)
- Single dose
80% efficacy preventing severe disease