Respiratory syncytial virus infection

Overview 
Theory 
Diagnosis 
Management 
Follow up 
Resources 

The suspicion for respiratory syncytial virus (RSV) can generally be entertained based on the season, history, and physical exam. However, numerous viruses cause similar symptoms and have been linked to bronchiolitis.[84] While a definitive diagnosis can be confirmed only by laboratory testing, this is not routinely recommended.[2]

Clinical features

RSV infection almost always produces symptoms. The severity varies depending on the patient's age, history of previous infection, and comorbidities.[43][85]

Clinicians should determine whether the patient is at high risk for developing severe illness, including the following factors:[1][15][16][17][18][45] [86]

History of prematurity

Age <6 months at the start of RSV season

Chronic lung disease

Complex congenital heart disease

Immune deficiency

These patients require closer observation and are frequently admitted to the hospital.[2]

Infants and young children

Infants typically present with upper respiratory tract findings such as rhinorrhea and congestion. The physician may suspect RSV as the diagnosis when, over the next 2-4 days, the lower respiratory tract becomes involved and illness manifests as tachypnea, cough, wheeze, prolonged expiration, and increased work of breathing.

Signs of moderate illness include hypoxemia (oxygen saturations <90%), tachypnea, increased work of breathing (nasal flaring, intercostal retractions, head bobbing), inadequate feeding, and dehydration. More-severe cases are associated with hypoxia and respiratory failure.[2][43]

Physicians should inquire about difficulty with feeding, malaise, and signs of otitis media, as these may also be present. Apnea may be the sole presenting finding in very young infants (age <1 month) and may be severe enough to result in death.[87] Very young infants may also present with sepsis.

Older children and adults

RSV disease in older children and healthy adults is typically limited to the upper respiratory tract but may progress to tracheobronchitis.[88] Symptoms include nasal congestion, ear and sinus involvement, productive cough, and wheezing.[88]

In young adults who are otherwise well, RSV typically presents as an upper respiratory tract infection with mild to moderate symptoms, and only very rarely causes severe disease.[89] Additionally, healthy children and adults may be asymptomatic facilitating the spread of infection to more vulnerable hosts.[90]

Immune deficiency, increasing age, and comorbidity

Older people, people with immune deficiency, and those with respiratory or cardiac comorbidity, are at risk for developing severe lower respiratory disease.[89][91]

Among immune deficient patients, the greatest incidence of RSV infection is seen in patients receiving hematopoietic stem cell transplants and lung transplants.[29] Patients with RSV receiving hematopoietic stem cell transplants develop progression from upper to lower respiratory tract infection in 40% to 60% of cases; in these patients, lower respiratory tract infection is associated with mortality rates of up to 80%.[29]

Diagnostic tests

Rapid point-of-care tests for the detection of RSV have a sensitivity and specificity of 75% and 99%, respectively.[92] However, the American Academy of Pediatrics (AAP) recommends that the diagnosis of bronchiolitis should be established based on findings in the history and physical exam.[2] The AAP further recommends that clinicians should not routinely order laboratory or radiographic studies for diagnosis.[2] Likewise, studies in adult populations have not proved to be of benefit.[8][93] The AAP does not recommend ordering routine virologic tests for RSV unless an infant receiving monthly prophylaxis is hospitalized with bronchiolitis.[2]

Nonetheless, confirming the presence of RSV may be advantageous in order to isolate and cohort patients with known infection.[94] Rapid viral testing has been shown to reduce the number of chest radiographs undertaken in the emergency department, and results suggest a beneficial effect in terms of lowering antibiotic usage, although this was not statistically significant.[95] [ ]

Testing of nasopharyngeal aspirates for RSV is available through rapid antigen testing (often available for use at the point-of-care) as well as polymerase chain reaction (PCR) testing. PCR testing has a higher sensitivity and equivalent specificity as compared with antigen testing, especially in the adult population where antigen test sensitivity can be as low as 50%.[96] Increasing availability and speed of PCR-based tests have made these more commonly used.[97]

If viral testing is indicated, do not order broad respiratory pathogen panels (including comprehensive viral panel testing) unless the result will affect patient management.[98][99]

Pulse oximetry

Pulse oximetry is readily available in most clinical settings. It is a rapid and accurate method for evaluating hypoxemia. Measuring oxygen saturation using pulse oximetry should be carried out in every baby and child presenting to secondary care with clinical evidence of bronchiolitis.[2][51] Do not use continuous pulse oximetry in children unless they are receiving supplemental oxygen.[100]

Disease severity is characterized by the following:

Mild illness: no hypoxemia. May have mildly increased respiratory rate, but retains ability to feed adequately.
Moderate illness: hypoxemia (oxygen saturations <90% to 92%), tachypnea, increased work of breathing (nasal flaring, intercostal retractions, head bobbing), inadequate feeding, and dehydration.
Severe illness: refractory hypoxemia, progressive respiratory distress, or frank respiratory failure.

Other testing

Chest radiograph may reveal atelectasis, hyperexpansion, and peribronchial cuffing.[101][102][103] Interstitial infiltrates are less common. Chest radiography should be reserved for patients with severe disease, and those who do not improve at the expected rate.[2][Figure caption and citation for the preceding image starts]: AtelectasisFrom the personal collections of Melvin L. Wright, DO and Giovanni Piedimonte, MD; used with permission [Citation ends]. com.bmj.content.model.Caption@339da15d [Figure caption and citation for the preceding image starts]: Air trapping and peribronchial cuffingFrom the personal collections of Melvin L. Wright, DO and Giovanni Piedimonte, MD; used with permission [Citation ends].

Complete blood count and serum chemistries are not routinely helpful but may be considered in the presence of severe disease. Blood cultures are indicated if bacterial infection is suspected.

Clinically assess the hydration status of babies and children with bronchiolitis to determine the hydration requirements of the patient.[51]

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