Approach

The suspicion for respiratory syncytial virus (RSV) can generally be entertained based on the season, history, and physical examination. However, numerous viruses cause similar symptoms and have been linked to bronchiolitis.[81] 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.[44][82]

Clinicians should determine whether the patient is at high risk for developing severe illness, including the following factors:[1][15]​​​​​​[16]​​​[17][18][46]​​​[83]

  • 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 rhinorrhoea 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 tachypnoea, cough, wheeze, prolonged expiration, and increased work of breathing.

Signs of moderate illness include hypoxaemia (oxygen saturations <90%), tachypnoea, 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][44]

Physicians should enquire about difficulty with feeding, malaise, and signs of otitis media, as these may also be present. Apnoea may be the sole presenting finding in very young infants (age <1 month) and may be severe enough to result in death.[84] 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.[85] Symptoms include nasal congestion, ear and sinus involvement, productive cough, and wheezing.[85]

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.[86] Additionally, healthy children and adults may be asymptomatic facilitating the spread of infection to more vulnerable hosts.[87]

Immune deficiency, increasing age, and comorbidity

Older people, people with immune deficiency, and those with respiratory or cardiac comorbidity, are at risk of developing severe lower respiratory disease.[86][88]

Among immune deficient patients, the greatest incidence of RSV infection is seen in patients receiving haematopoietic stem cell transplants and lung transplants.[30] Patients with RSV receiving haematopoietic 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%.[30]

Diagnostic tests

Rapid point-of-care tests for the detection of RSV have a sensitivity and specificity of 75% and 99%, respectively.[89] However, the American Academy of Pediatrics (AAP) recommends that the diagnosis of bronchiolitis should be established based on findings in the history and physical examination.[2] The AAP further recommends that clinicians should not routinely order laboratory or radiographical studies for diagnosis.[2] Likewise, studies in adult populations have not proved to be of benefit.[8][90]

Nonetheless, confirming the presence of RSV may be advantageous in order to isolate and cohort patients with known infection.[91] Rapid viral testing has been shown to reduce the number of chest radiographs undertaken in the accident and emergency department, and results suggest a beneficial effect in terms of lowering antibiotic usage, although this was not statistically significant.[92] [ Cochrane Clinical Answers logo ] ​ 

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%.[93] Increasing availability and speed of PCR-based tests have made these more commonly used.[94]

Pulse oximetry

Pulse oximetry is readily available in most clinical settings. It is a rapid and accurate method for assessing hypoxaemia. 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][53]

Disease severity is characterised by the following:

  • Mild illness: no hypoxaemia. May have mildly increased respiratory rate, but retains ability to feed adequately.

  • Moderate illness: hypoxaemia (oxygen saturations <90% to 92%), tachypnoea, increased work of breathing (nasal flaring, intercostal retractions, head bobbing), inadequate feeding, and dehydration.

  • Severe illness: refractory hypoxaemia, progressive respiratory distress, or frank respiratory failure.

The National Institute for Health and Care Excellence recommends assessing a baby or child in a secondary care setting, and admitting them to hospital if they have any of the following:[53]

  • apnoea (observed or reported)

  • persistent oxygen saturation (when breathing air) of:

    • less than 90%, for children aged 6 weeks and over

    • less than 92%, for babies under 6 weeks or children of any age with underlying health conditions

  • inadequate oral fluid intake (50% to 75% of usual volume, taking account of risk factors and using clinical judgement)

  • persisting severe respiratory distress i.e., grunting, marked chest recession, or a respiratory rate of over 70 breaths/minute.

Other testing

Chest radiograph may reveal atelectasis, hyperexpansion, and peribronchial cuffing.[95][96][97] 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@615f14fb[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].com.bmj.content.model.Caption@5b6d08c4

The National Institute for Health and Care Excellence recommends only performing a chest x‑ray if intensive care is being proposed for a baby or child. A chest x‑ray in babies or children with bronchiolitis may mimic pneumonia and should not be used to determine the need for antibiotics.[53] 

Full 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.[53]

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