Respiratory syncytial virus infection

Respiratory syncytial virus (RSV) is an enveloped RNA virus that infects the respiratory tract. RSV is one of the most common causes of respiratory infections. In healthy adults and older children, RSV typically manifests as a mild upper respiratory tract infection (URTI). Infants, young children, older adults, and individuals with other risk factors for severe RSV infection are more likely to develop a lower respiratory tract infection (LRTI) and/or require hospitalization. RSV-associated conditions are typically diagnosed clinically without the need for pathogen confirmation. Diagnostic testing (e.g., RSV PCR, chest x-ray) may be indicated in individuals with severe illness, risk factors for severe RSV infection, or suspected alternative diagnoses or complications. Management is generally supportive and focuses on the treatment of the associated condition. Primary prevention includes the RSV vaccine (for pregnant individuals and older adults) and RSV prophylaxis (for infants and young children).

See also “Bronchiolitis.”

• Almost all individuals have had an RSV infection by 2 years of age and reinfection can occur throughout life. ^[1]
• A significant cause of morbidity and mortality in young children and older adults
  • The most common cause of hospitalization, bronchiolitis, and pneumonia in infants ^[2][3]
  • Responsible for ∼ 20% of all ER visits in children < 5 years of age ^[1]
  • Results in up to 160,000 hospitalizations and up to 10,000 deaths in older adults each year. ^[4]

RSV morbidity and mortality rates follow a bimodal age distribution; infants, young children, and older adults are most severely affected. ^[2]

Epidemiological data refers to the US, unless otherwise specified.

• The RSV virus is an enveloped, nonsegmented, negative-stranded RNA virus ^[5]
  • Pneumoviridae family, Orthopneumovirus genus, Human orthopneumovirus species ^[5][6]
  • Has two antigenic subtypes: A and B ^[5]
• Virulence factors
  • Glycoprotein G: mutates often ^[2][5]
  • RSV fusion (F) protein: typically conserved ^[5]
• Transmission
  • Transmitted via direct contact with respiratory droplets and indirect contact with contaminated surfaces ^[1][5][7]
  • The incubation period is 2–8 days. ^[1][5][7]
  • Viral shedding typically lasts 3–8 days. ^[1][5][7]
  • In the US, RSV season has historically occurred from fall through early spring. ^[8][9]

The RSV vaccine targets the RSV fusion (F) protein, as it rarely mutates. ^[5]

The following risk factors are associated with severe RSV infections, typically LRTIs.

Risk factors for severe RSV infection in children ^{[5][10][11][12]}

• Chronological age < 6 months (single most important risk factor) ^[10]
• Comorbidities ^[10]
  • Preterm birth, especially if associated with chronic lung disease of prematurity
  • Congenital heart disease
  • Immunocompromised state
  • Neuromuscular disorders that affect the ability to clear airway secretions
• Environmental factors ^[10]
  • Childcare attendance
  • Exposure to tobacco smoke ^[13]
• For information on RSV prevention in children with risk factors, see “RSV prophylaxis.”

Most children who are hospitalized with RSV infection are otherwise healthy with no previous medical conditions. ^[2][14]

Risk factors for severe RSV infection in adults ^[4]

• Older age: ≥ 60 years (especially ≥ 75 years) ^[4]
• Comorbidities, e.g.: ^[15]
  • Chronic lung diseases: COPD, asthma
  • Cardiac diseases: congestive heart failure, coronary artery disease
  • Neurologic disorders: cerebrovascular disease, neuromuscular conditions
  • Diabetes mellitus
  • Chronic kidney disease
  • Liver disease
  • Hematologic disorders
  • Immunocompromised state, e.g., from medical conditions or use of medications
• Living in a long-term care facility
• Reduced functional capacity or frailty
• For information on RSV prevention in adults with risk factors, see “RSV vaccine” and “Immunization schedule.”

• Symptoms of nonspecific viral illness ^[5][7]
  • Lethargy or fatigue
  • Irritability
  • Decreased appetite
  • Fever
• Symptoms of upper respiratory tract infection ^[1][5][7]
  • Rhinorrhea is often thick and copious in infants. ^[16]
  • Acute otitis media occurs in up to 60% of children with RSV. ^[1]
• Symptoms of lower respiratory tract infection ^[1][5][7]
  • All patients: cough, tachypnea, rales, wheezes, crackles
  • In young children: clinical features of bronchiolitis, clinical features of pediatric pneumonia
  • In older children and adults: clinical features of acute bronchitis, clinical features of pneumonia
  • Signs of severe RSV infection: signs of respiratory distress, hypoxemia, and, in young infants, apnea ^[1]

Diagnostic testing for RSV is not routinely indicated but can be considered depending on clinical features. ^[5][17]

Approach ^[1][5][17]

• Consider confirmatory testing for: ^[1]
  • Patients with risk factors for severe RSV infection
  • Hospital admission infection control ^[5]
• Obtain additional studies (e.g., ABG, respiratory viral panel, chest x-ray) for severe illness. ^[1]
• In children, see also “Diagnostics of bronchiolitis” and “Diagnostics of pediatric pneumonia.”
• In adults, see also “Diagnostics for acute bronchitis” and “Diagnostics of pneumonia.”

Confirmatory testing ^[5][17][18]

If indicated, RSV can be identified in samples from the upper or lower respiratory tract using any of the following:

• Nucleic acid amplification test, e.g., reverse transcription PCR (preferred) ^[5][17]
• Rapid antigen detection test (young children only) ^[5][17]
• Viral culture (rarely used) ^[5]

Chest x-ray ^[1][9]

Radiography is not routinely indicated. Findings may include the following: ^[1]

• Nonspecific findings: peribronchial thickening, pulmonary hyperinflation
• Chest x-ray findings in bronchiolitis
• Chest x-ray findings in pneumonia

Management depends on disease presentation and severity.

Approach ^[5][17][19]

• All patients
  • Provide supportive care.
  • Screen for risk factors for severe RSV infection.
  • Assess for indications for pharmacotherapy.
• Mild RSV infection
  • Outpatient management
  • Discuss return precautions for signs of severe RSV infection, dehydration, or signs of a secondary bacterial infection. ^[20]
• Severe RSV infection: Admission may be required for respiratory support. ^[1][5]
• If admitted, initiate contact precautions for the following patients: ^[5][21][22]
  • Infants and young children
  • Immunocompromised individuals

RSV viral shedding can be prolonged ≥ 3 weeks in certain individuals, e.g., infants and immunocompromised individuals; extended contact precautions may be necessary. ^[1][5][7]

Supportive care ^[5][17][19]

• Cool mist humidifier or steamy showers
• Antipyretics for fever and/or discomfort
• Encourage adequate fluid intake; if unable to tolerate oral fluids, provide NG/IV fluids.
• Gentle nasal suctioning in infants
• In children, see also:
  • Management of bronchiolitis
  • Management of pneumonia in children
  • Supportive care for pediatric fever
• In adults, see also:
  • Management of acute bronchitis
  • Management of pneumonia

Pharmacotherapy

• Antibiotics: only indicated for a confirmed bacterial coinfection or superinfection ^[1][5][18]
• RSV-directed therapies (rarely used): Consult infectious disease for patients with severe RSV pneumonia or an immunocompromised state. ^[5][17][18]
  • Infants and young children: inhaled ribavirin ^[5][17][18]
  • RSV immunoglobulin (off-label)

General principles ^[1][5]

• Recommend the RSV vaccine in older adults. ^[4]
• To decrease the risk of infection in children, encourage:
  • RSV vaccination during each pregnancy ^[23]
  • Exclusive breastfeeding for infants ^[1]
  • RSV prophylaxis for eligible young children
  • Avoidance of tobacco smoke exposure ^[1][5]
• See also “Preventing transmission of respiratory infections.”

RSV vaccine (adults) ^[23][24]

• Description: a bivalent vaccine based on the prefusion form of the RSV fusion (F) protein ^[25]
• Indications
  • All pregnant individuals between 32 and 36 weeks' gestation ^[23]
  • All individuals ≥ 75 years of age ^[24]
  • Individuals ≥ 60 years of age with adult risk factors for severe RSV infection ^[24]
• Additional information
  • Immunization schedule
  • Immunizations in pregnancy

RSV prophylaxis (children) ^[12][26][27]

• Monoclonal antibodies that target the RSV fusion (F) protein are used to provide passive immunization.
• RSV prophylaxis reduces RSV-related hospitalizations (e.g., due to bronchiolitis, pneumonia) in infants.
• Two RSV monoclonal antibodies are now available.
  • Nirsevimab (preferred)
    • A long-acting RSV monoclonal antibody that provides protection for 5 months
    • Administered as a single intramuscular injection during or, preferably, just before RSV season
  • Palivizumab (alternative) ^[11][12]
    • A short-acting RSV monoclonal antibody
    • Administered as monthly intramuscular injections
    • Initiate administration just before and continue throughout the RSV season. ^[12]
    • In children with RSV-related hospitalization, discontinue for the remainder of the current RSV season. ^[12]

If available, nirsevimab is preferred over palivizumab because it can be administered as a single dose rather than monthly dosing. ^[26]

Palivizumab and nirsevimab provide RSV (Pneumovirus) Prophylaxis for Preexisting conditions (e.g., Preterm).

RSV prophylaxis can be administered at the same visit as other age-appropriate vaccines. ^[26]