Basics
Description
- An enveloped, nonsegmented RNA virus of the family Paramyxoviridae and in the subfamily Pneumovirinae along with human metapneumovirus. There are 2 subgroups, A and B, differentiated by the major attachment G protein, a large surface glycoprotein. The fusion or F protein is relatively homologous between the 2 subgroups.
- It is the most common cause of bronchiolitis, a lower respiratory tract disease that primarily affects the small airways.
Epidemiology
- Incubation period is 2 " 8 days.
- Virus is detected in secretions 4 days prior to clinical symptoms. Typically shedding of infectious virions is 3 " 8 days but can be as long as 3 " 4 weeks in immunocompromised.
- Transmission occurs by direct contact of nasopharyngeal or ocular mucosa with infected secretions or fomites.
- Nosocomial spread can occur because the virus can survive on surfaces and hands for several hours.
- In the United States, epidemics typically occur between November and April and last for roughly 18 " 20 weeks.
- In tropical climates, respiratory syncytial virus (RSV) seasons are less predictable and can circulate year-round.
- One antigenic strain predominates during any given epidemic, but both subtypes can circulate concurrently.
Incidence
- Peak incidence is the first 2 years of life. 20 " 30% of infected infants develop lower respiratory tract disease.
- Annual rate of RSV-associated hospitalization is roughly 3/1,000 in children <5 years of age and 17/1,000 in children <6 months of age.
Prevalence
- 50% of children are infected by their 1st birthday. 100% of children are infected by age of 2 years.
- Reinfection can occur during the same RSV season and is common during the first few years of life.
- Subsequent infections are typically milder.
Risk Factors
Those at greatest risk for severe infection include:
- Children <1 year of age, especially those <6 months of age
- Children born prematurely (<35 weeks gestation)
- Children with underlying cardiopulmonary disease (e.g., chronic lung disease of prematurity, congenital heart disease)
- Those with primary immune deficits
- Patients on immunosuppressive medications (e.g., transplant patients, oncology patients)
General Prevention
- There is currently no RSV vaccine. A formalin-inactivated RSV vaccine tested in the 1960s caused enhanced illness after reexposure to wild-type RSV likely due to an overexuberant immune response.
- Because RSV can survive on surfaces, strict hand washing can minimize nosocomial spread.
- Contact isolation with routine usage of gowns and gloves has been shown to decrease RSV nosocomial spread.
- Patients with RSV infection should be isolated in private rooms.
- Palivizumab, a humanized monoclonal antibody directed against the highly conserved F protein of RSV, is the only product available for the prevention of RSV infection in certain high-risk children.
- Children who should receive palivizumab:
- Children <2 years of age who receive medical therapy for chronic lung disease
- Infants with a history of prematurity (birth at <32 weeks gestation)
- Children for whom palivizumab should be considered:
- High-risk premature infants born between 32 and 35 weeks ' gestation
- Infants with congenital heart disease, congenital airway abnormalities, or neuromuscular disease
- Palivizumab is given IM (15 mg/kg) every 30 days for 5 doses usually from November to April.
- Specific recommendations are available from the American Academy of Pediatrics (AAP) Committee on Infectious Diseases and Committee on Fetus and Newborn.
Pathophysiology
- The G protein is the major surface glycoprotein responsible for attachment of virus to cells.
- The F protein aids in viral entry in to cells and is responsible for fusion of adjacent cells to form a syncytia.
- Infection is initiated in nasopharynx and then can move to the lower respiratory tract.
- Infection of smaller airways leads to edema and necrosis of epithelial cells and infiltration of inflammatory cells, resulting in airway obstruction and air trapping.
- Severe RSV infection has been associated with recurrent wheezing later in life. It is unclear whether RSV infection causes subsequent wheezing or if patients predisposed to severe wheezing are more likely to have severe RSV disease.
Diagnosis
History
- Initial symptoms include copious nasal discharge, cough, and fever.
- Cough is the most common symptom typically progressing over 1 " 2 days.
- Concerning findings on history:
- Apnea, severe coughing with possible cyanotic episodes
- Poor oral intake
- Decreased urine output (e.g., fewer wet diapers)
- Trouble breathing
Physical Exam
- Profuse rhinorrhea
- Acute otitis media or otitis media with effusion
- Signs of dehydration (dry mucus membranes, delayed capillary refill time)
- Conjunctivitis
- Varying levels of respiratory distress:
- Mild: suprasternal retractions, mild tachypnea
- Moderate: subcostal or intracostal retractions
- Severe: severe retractions, grunting, RR >60, lethargy
- Air trapping resulting in hyperexpansion of lungs can lead to a barrel-shaped chest, palpable liver, or spleen below the costal margin.
- Pulse oximetry may reveal hypoxemia.
Diagnostic Tests & Interpretation
Lab
- A definitive diagnosis of RSV can be made by viral culture but requires up to 5 days.
- Rapid diagnostic antigen assays from nasopharyngeal specimens are used for RSV detection, usually with a sensitivity of 80 " 90%:
- Enzyme immunoassay
- Immunofluorescent assay
- Reverse transcriptase-polymerase chain reaction (RT-PCR) assays are commercially available and may have superior sensitivity to rapid antigen testing. However, these assays detect viral RNA that may persist in nasal secretions after patient is no longer shedding infectious virus.
- Because concurrent serious bacterial infections are not common, complete blood counts or blood cultures are not indicated.
- Given reported 3% incidence of concurrent urinary tract infections (UTIs), urinalysis and urine culture can be considered for infants with persistent fever.
Imaging
- Chest x-rays should not be routinely obtained in children with RSV.
- Often reveals hyperinflation, increased bronchial markings, and areas of atelectasis/infiltrates, findings which may not alter the treatment plan or may in some cases lead to unnecessary antibiotics.
Differential Diagnosis
- Infection
- Influenza virus
- Parainfluenza virus
- Human metapneumovirus
- Adenovirus
- Coronaviruses
- Mycoplasma pneumoniae
- Environmental: foreign body in upper airway
- Tumors: mass compressing upper airway
- Congenital: laryngomalacia or tracheomalacia
Treatment
Medication
- ²-Adrenergic agents: Bronchodilators should not be used routinely. However, there are some data to suggest that they may lead to transient improvement in respiratory scores in some patients, but no data that suggests that this impacts hospitalization rates or length of stay.
- Racemic epinephrine: Racemic epinephrine has been demonstrated to reduce hospital admission rates compared to placebo and to shorten length of stay when compared to albuterol.
- Select patients may benefit from a trial of bronchodilators, but this remains controversial. Careful attention should be paid to the clinical exam before and after administration to support their ongoing use.
- Corticosteroids are not useful in bronchiolitis and should not be used.
- Ribavirin: has in vitro antiviral activity against RSV, but ribavirin aerosol treatment for RSV infections should not be used routinely in the treatment of children with bronchiolitis. There may be some benefit in severely ill patients such as immunocompromised patients with severe disease.
- Antibiotics are rarely indicated because concurrent bacterial disease (lung or blood) is uncommon in patients with RSV bronchiolitis. However, 3% of patients with bronchiolitis and fever have urine culture findings consistent with UTI.
- There is limited evidence that nebulized hypertonic saline (3%) may reduce length of hospital stay and improve clinical symptoms.
Additional Therapies
General Measures
- Supportive care: hydration therapy and supplemental oxygen as needed if oxygen saturation persistently falls below 90%
- Cardiorespiratory monitoring and pulse oximetry should be used for infants at risk for apnea and hypoxemia.
- In severe cases, respiratory support with continuous positive airway pressure (CPAP) or mechanical ventilation is required.
Inpatient Considerations
Initial Stabilization
Apnea or severe respiratory distress with impending respiratory failure may require intubation and mechanical ventilation.
Ongoing Care
Follow-up Recommendations
- Lower respiratory tract symptoms usually arise 2 " 3 days after initial symptoms.
- Symptoms usually peak from 5 to 7 days, but 20% of children can have symptoms for 3 weeks.
- Recurrent apneic episodes are rare, and home monitoring is usually not indicated.
- Fever commonly resolves over 2 " 3 days.
Patient Monitoring
Signs to watch for:
- Increased respiratory rate and increased work of breathing
- Lethargy, altered mental status
- Signs and symptoms of dehydration (dry mucous membranes, decreased urine output)
Prognosis
- Most children have a mild to moderate disease course requiring only supportive care.
- Approximately 1 " 3% of children will require hospitalization. Most children recover with no sequelae.
- Infants born prematurely or with underlying cardiopulmonary disease are at increased risk for more severe and longer duration of disease.
- Reinfections occur throughout life with an incidence of about 5% per year.
- There are some data to suggest that patients with severe RSV bronchiolitis may have more episodes of recurrent wheezing in the 1st year of life. It is unclear whether severe RSV infection causes long-term airway hyperresponsiveness.
Complications
- Dehydration
- Apneic episodes in young infants (can occur in all causes of bronchiolitis, not just RSV)
- Hypoxemia
- Hypercarbia
- Respiratory failure
- Pneumonia, rarely bacterial
- Croup
- Acute otitis media
- Asthma
Additional Reading
- American Academy of Pediatrics. Respiratory syncytial virus. In: Pickering LK, Baker CJ, Kimberlin DW, et al, eds. Red Book: 2012 Report of the Committee on Infectious Diseases. 29th ed. Elk Grove Village, IL: American Academy of Pediatrics; 2012:609 " 618.
- American Academy of Pediatrics Subcommittee on Diagnosis and Management of Bronchiolitis. Diagnosis and management of bronchiolitis. Pediatrics. 2006;118(4):1774 " 1793. [View Abstract]
- Hall CB, Weinberg GA, Iwane MK, et al. The burden of respiratory syncytial virus infection in young children. N Engl J Med. 2009;360(6):588 " 598. [View Abstract]
- Zhang L, Mendoza-Sassi RA, Wainwright C, et al. Nebulized hypertonic saline solution for acute bronchiolitis in infants. Cochrane Database Syst Rev. 2008;(4):CD006458. [View Abstract]
Codes
ICD09
- 079.6 Respiratory syncytial virus (RSV)
- 466.11 Acute bronchiolitis due to respiratory syncytial virus (RSV)
ICD10
- B97.4 Respiratory syncytial virus causing diseases classd elswhr
- J21.0 Acute bronchiolitis due to respiratory syncytial virus
- J20.5 Acute bronchitis due to respiratory syncytial virus
SNOMED
- 55735004 Respiratory syncytial virus infection (disorder)
- 57089007 respiratory syncytial virus bronchiolitis (disorder)
- 195727009 Acute respiratory syncytial virus bronchitis
FAQ
- Q: How did my child get this illness?
- A: RSV bronchiolitis is caused by respiratory syncytial virus, an extremely common virus which is passed from one person to another by contact with nasal secretions and through airborne transmission of droplets.
- Q: For how long is my child contagious?
- A: Viral shedding occurs for 24 hours prior to the onset of clinical symptoms and for up to 21 days from the onset of symptoms.
- Q: Will my child develop asthma because of the wheezing that is occurring now?
- A: There is an association between severe RSV bronchiolitis and recurrent wheezing episodes during the 1st year of life. However, it is not clear whether RSV causes asthma later in life.
- Q: How do I prevent my child from being infected with RSV?
- A: Unfortunately, there is no vaccine against RSV. In high-risk infants (infants born prematurely with chronic lung disease, congenital heart disease) palivizumab can be administered during RSV season to prevent severe lower respiratory tract disease.