Bronchiolitis

Bronchiolitis is inflammation of the bronchioles, the smallest air passages of the lungs. It usually occurs in children less than two years of age with the majority being aged between three and six months.

Bronchiolitis chest X-ray

Signs and symptoms

In a typical case, an infant under two years of age develops cough, wheeze, and shortness of breath over one or two days. Crackles and/or wheeze are typical findings on listening to the chest with a stethoscope. The infant may be breathless for several days. After the acute illness, it is common for the airways to remain sensitive for several weeks, leading to recurrent cough and wheeze.

Some signs of severe disease include:

• poor feeding (less than half of usual fluid intake in preceding 24 hours)
• lethargy
• history of apnea
• respiratory rate >70/min
• presence of nasal flaring and/or grunting
• severe chest wall recession
• cyanosis

Respiratory bronchiolitis

Causes

• The term usually refers to acute viral bronchiolitis, a common disease in infancy.
• This is most commonly caused by respiratory syncytial virus
• Respiratory syncytial virus (RSV) was discovered in 1956 and has since been recognized as one of the most common causes of childhood illness.
• It causes annual outbreaks of respiratory illnesses in all age groups.
• In most regions of the United States, RSV usually circulates during fall, winter, and spring, but the timing and severity of RSV season in a given community can vary from year to year.

Clinical Laboratory Testing

• Clinical symptoms of RSV are nonspecific and can overlap with other viral respiratory infections, as well as some bacterial infections.
• Several types of laboratory tests are available for confirming RSV infection.
• These tests may be performed on upper and lower respiratory specimens.
• The most commonly used types of RSV clinical laboratory tests are real-time reverse transcriptase-polymerase chain reaction (rRT-PCR), which is more sensitive than culture and antigen testing antigen testing, which is highly sensitive in children but not sensitive in adults
• Less commonly used tests include viral culture serology, which is usually only used for research and surveillance studies
• Some tests can differentiate between RSV subtypes (A and B), but the clinical significance of these subtypes is unclear.

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Bronchiolitis obliterans

For Infants and Young Children

• Both rRT-PCR and antigen detection tests are effective methods for diagnosing RSV infection in infants and young children.
• The RSV sensitivity of antigen detection tests generally ranges from 80% to 90% in this age group.
• Healthcare professionals should consult experienced laboratorians for more information on interpretation of results.

For Older Children, Adolescents, and Adults

• Healthcare professionals should use highly sensitive rRT-PCR assays when testing older children and adults for RSV.
• rRT-PCR assays are now commercially available for RSV.
• The sensitivity of these assays often exceeds the sensitivity of virus isolation and antigen detection methods.
• Antigen tests are not sensitive for older children and adults because they may have lower viral loads in their respiratory specimens.
• Healthcare professionals should consult experienced laboratorians for more information on interpretation of results.

Prophylaxis and High-Risk Infants and Young Children

• Palivizumab is a monoclonal antibody recommended by the American Academy of Pediatrics (AAP) to be administered to high-risk infants and young children likely to benefit from immunoprophylaxis based on gestational age and certain underlying medical conditions.
• It is given in monthly intramuscular injections during the RSV season, which generally occurs during fall, winter, and spring in most locations in the United States.

Bronchiolitis Resources
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