Respiratory Syncytial Virus (RSV) Infection
Respiratory syncytial virus (RSV) is a medium-sized, membrane-bound RNA virus that causes acute respiratory tract illness in patients of all ages.
- In adults, RSV causes upper respiratory tract infection (URTI).
- In infants and children, RSV commonly presents as lower respiratory tract infection (LRTI) that manifests as bronchiolitis and rarely pneumonia, respiratory failure, and death.
90–95% of children are infected by 24 months; leading cause of pediatric bronchiolitis (50–90%); premature infants and infants aged <6 months are at increased risk.
- Outbreaks of RSV disease occur each winter (October to late January).
- Morbidity and mortality:
- RSV infection leads to >100,000 annual hospitalizations. In the United States, 2.1 million outpatient visits for RSV in children aged <5 years.
- Worldwide, RSV is responsible for approximately 33 million LRTI/year and up to 199,000 childhood deaths.
- Annually, RSV causes an estimated 33.1 million acute LRTI worldwide, and 3.2 million hospitalizations in children aged <5 years.
- RSV cases are particularly increasing in the wake of the COVID-19 pandemic.
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Etiology and Pathophysiology
- RSV is a single-stranded, negative-sense RNA virus belonging to the Paramyxoviridae family.
- Two subtypes, A and B, are simultaneously present in most outbreaks with A subtypes causing more severe disease.
- RSV is spread via direct contact or droplet aerosols. Incubation period ranges from 2 to 8 days, mean 4 to 6.
- Natural RSV infections result in incomplete immunity; recurrent infections are common.
- RSV causes a neutrophil-intensive inflammation of the airway. RSV develops in the cytoplasm of infected cells and matures by budding from the plasma membrane. RSV is a major cause of exacerbation of asthma and chronic obstructive pulmonary disease (COPD).
- Severe RSV infections may be associated with polymorphisms in cytokine-related genes, including CCR5; IL4; IL8, IL10, and IL13.
- RSV replicates in apical ciliated bronchial epithelial cells. The airway epithelium produces chemokines, which recruit neutrophils.
Significant association with RSV-associated acute LRTI
- Infants born before the 35 weeks’ gestation; low birth weight, male gender; underlying cardiopulmonary disease; HIV; Down syndrome
- Any age group with persistent asthma; children aged <5 years with socioeconomic vulnerability; immunodeficiency; siblings with asymptomatic RSV infection; secondhand smoke; history of atopy, no breastfeeding; adult patients with COPD or functional disability
- Other risk factors
- Daycare center attendance; exposure to indoor and environmental air pollutants; multiple births, malnutrition, higher altitude
- Isolate patients with proven or suspected RSV.
- Palivizumab is a humanized monoclonal antibody for the prevention of severe RSV in high-risk children (2)[A]:
- Preterm infants born ≤28 weeks, 6 days of gestation, or who are <12 months of age at start of RSV season; infants with bronchopulmonary dysplasia who are <1 year or <23 months of age and requiring treatment; infants ≤12 months of age who are being medically treated for acyanotic heart disease or have moderate to severe pulmonary hypertension
- A single injection of nirsevimab administered before the RSV season protected healthy late-preterm and term infants from medically attended RSV-associated LTRI. Target populations for immunization include older infants, young children (e.g., those born prematurely or with cardiopulmonary disease or immunodeficiency), and high-risk adults (e.g., those aged ≥65 years).
- Nirsevimab offers a large advantage over current therapy with palivizumab, which has an involved treatment regimen of 5 monthly doses.
- Probiotics protect against RSV infection in neonatal mice through a microbiota-AM axis, suggesting that the probiotics may be a promising candidate to prevent and treat RSV infection, and deserve more research and development in the future.
- Prophylactic use is indicated for infants and children <24 months of age with:
- Chronic lung disease (CLD) of prematurity
- Hemodynamically significant congenital heart disease
- Congenital abnormalities of the airway or neuromuscular disease
- Preterm infants born <29 weeks’ gestational age (WGA) and <1 year of age at the RSV season start date; infants in the 1st year of life with CLD of prematurity; infants with HS-CHD <1 year of age at the season start date
- Dosage: maximum of 5 monthly doses beginning in November or December at 15 mg/kg per dose IM
- Breastfeeding can significantly reduce hospitalizations due to respiratory infections.
Commonly Associated Conditions
In hospitalized infants:
- Pulmonary infiltrates/atelectasis (42.8%); otitis media (25.3%); hyperinflation (20.8%); respiratory failure (14%)
- Hyperkalemia (10.1%, defined as K+ >6.0); apnea (8.8%); bacterial pneumonia (7.6%)
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