Respiratory syncytial virus (RSV) affects infants, young children, and older adults, particularly those with compromised respiratory or cardiovascular health. Every year RSV causes approximately 58,000 to 80,000 hospitalizations and 100 to 300 deaths in children aged less than 5 years, as well as 60,000 to 160,000 hospitalizations and 6,000 to 10,000 deaths among adults aged 65 years and older.1
Most recent studies reveal a high threat of this infection in the southeastern region of the United States. A landmark study on patients under the age of 5 years suggested that RSV infection is the single greatest causative factor of pneumonia in this age group in the US.2 In another study of adults aged 60 years and older hospitalized with RSV infection, 66% developed pneumonia.3
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Risk Factors and Transmission for RSV
In children, risk factors for infection include prematurity at birth, low birthweight (<2500 g), underlying immunologic disorders (either natural or acquired), genetic and chromosomal abnormalities (eg, Down syndrome), the presence of other pulmonary disease processes, neoplasias, and defects of the heart and/or lung structures. In older adults, immunosuppression, chronic obstructive pulmonary disease (COPD), and heart failure increase susceptibility to RSV infection.4
“Diagnosis of RSV is made by rapid antigen detection tests (RADTs), direct fluorescent antibody (DFA), polymerase chain reaction (PCR), and viral cultures of nasopharyngeal swabs and aspirates.”
Transmission of RSV takes place via droplets and contaminated surfaces. The virus can survive for many hours on hard surfaces such as tables and crib rails. Those infected with RSV are usually contagious for 3 to 8 days after showing symptoms. However, people can spread the disease in the prodromal phase, which is 1 to 2 days before demonstration of symptoms. Some infants and immunosuppressed adults can continue to spread the virus for as long as 4 weeks. Children are often exposed to and infected with RSV outside the home, such as in school or childcare centers.5
Clinical Manifestations of RSV
Symptoms of RSV infection include fever, cough, sneezing, and wheezing. Bronchiolitis is common in younger children with RSV. Clinically, bronchiolitis is characterized by expiratory breathing difficulty in infants. Other signs and symptoms include cough, tachypnea, hyperinflation, intercostal retractions, and wheezing.6 Pneumonia is a common sequela of RSV infection in both children and adults; it is most commonly evidenced by fever, cough, hypoxia, cyanosis, and pulmonary crackles. Infection can lead to complications that require supplemental oxygen, intensive care unit (ICU) admission, and mechanical ventilation. In older adults, particularly those over age 60 with underlying comorbidities, RSV can cause exacerbations of heart failure and COPD.3,7
Pathophysiologic Mechanism of RSV
In children, particularly in premature infants, the immaturity of the pulmonary immune system is partly responsible for increased susceptibility to RSV infection. A genetic predisposition may also play a role in the development of severe lower respiratory infection and hyper-reactivity of the airway. It is believed that the infant’s lungs are stimulated by a T-helper 2 cell inflammation reaction against RSV. There is a deficient response by interferons, which should naturally fight viruses, and increased response by the inflammatory mediators, interleukins. This results in goblet cell hyperplasia, increased mucus production, and bronchospasm.8,9
The mechanism by which RSV causes lower respiratory illness in older adults is less clear. Older adults are known to be less immunocompetent than younger adults and children. It is believed they possess lower RSV-specific serum immunoglobulin (Ig) and nasal IgA titers, which increases their susceptibility.10 Older patients with COPD have hyper-reactive airways and RSV, as well as other pathogens, can trigger an exacerbation. RSV infection causes mucous overproduction, reduced mucociliary clearance, and subsequent airway obstruction in those with COPD. Those with heart failure are in a precarious position where inflammation of the lungs can cause hypoxia, which can lead to decompensation of cardiac function.11 Importantly, natural infection does not provide long-lasting immunity to RSV and reinfections with RSV can occur throughout life.12
Diagnosis of RSV
Respiratory syncytial virus can be detected by rapid antigen detection tests (RADTs), direct fluorescent antibody (DFA), and polymerase chain reaction (PCR) testing on nasopharyngeal swabs and aspirates (Figure). Viral cultures can be done, however, turn-around time is up to 7 days. If RSV is the main concern, DFA testing or RADTs are most commonly recommended, particularly for infants and children. If other respiratory viruses are also of concern, PCR panels are available that test for a spectrum of respiratory viruses, including RSV. PCR testing is generally more reliable in adults and is recommended for all hospitalized or immunocompromised patients.13
Treatment of RSV
Treatment for RSV infection mainly includes supportive interventions to prevent dehydration, reduce fever, and manage airway obstruction. Intravenous fluids, bronchodilators, corticosteroids, and mucolytic agents can be used to relieve symptoms. Continual monitoring of oxygenation is necessary. Supplemental oxygen should be administered if needed. Mechanical ventilation may be required in severely affected individuals.
Prevention of RSV Infection
New prevention tools for RSV have become available according to the Centers for Disease Control and Prevention (CDC).14 These include monoclonal antibody agents and vaccines. Nirsevimab is a long-acting monoclonal antibody approved by the US Food and Drug Administration (FDA) to protect infants and young children at increased risk for severe RSV disease. Nirsevimab is safe and efficacious. In clinical trials, 1 dose of nirsevimab administered as an intramuscular injection protected infants for at least 5 months (the length of an average RSV season) and reduced the risk of severe RSV disease by about 80%.14
Another monoclonal antibody, palivizumab, is recommended by the American Academy of Pediatrics (AAP) for administration to infants and young children who are at increased risk of severe RSV disease. It is given in monthly intramuscular injections during RSV season.15
The FDA has approved two recombinant protein vaccines RSVPreF3 and RSVpreF that are approved by the FDA for use in adults aged 60 years and older to prevent RSV-associated lower respiratory tract disease. During the first RSV season after vaccination, each vaccine was more than 80% efficacious in preventing RSV-associated lower respiratory tract disease.16
On August 21, 2023, FDA approved the RSVpreF vaccine for use in pregnant women during weeks 32 through 36 of gestation for the prevention of RSV-associated lower respiratory tract disease in infants from birth through 6 months of age.17
Conclusion
Respiratory syncytial virus affects infants, young children, and older adults, particularly those with compromised respiratory or cardiovascular health. Most recent studies reveal a high threat of this infection in the southeastern region of the United States. Diagnosis of RSV is made by rapid antigen detection tests (RADTs), direct fluorescent antibody (DFA), and polymerase chain reaction (PCR) testing on nasopharyngeal swabs and aspirates. New prevention tools for RSV include monoclonal antibody agents and vaccines. These are proving to be highly efficacious and safe for children and adults.
