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Clinical Description and Diagnosis
Clinical Laboratory Testing
Prophylaxis and High-Risk Infants and Young Children

Healthcare providers should consider RSV in patients with respiratory illness, particularly during the RSV season.

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 circulation starts in the fall and peaks in the winter, but the timing and severity of RSV season in a given community can vary from year to year. Scientists are developing several vaccines, monoclonal antibodies, and antiviral therapies to help protect infants and young children, pregnant people (to protect their unborn babies), and older adults from severe RSV infection.

Clinical Description and Diagnosis

In Infants and Young Children

RSV infection can cause a variety of respiratory illnesses in infants and young children. It most commonly causes a cold-like illness but can also cause lower respiratory infections like bronchiolitis and pneumonia. One to two percent of children younger than 6 months of age with RSV infection may need to be hospitalized. Severe disease most commonly occurs in very young infants. Additionally, children with any of the following underlying conditions are considered at high risk:

Premature infants
Infants, especially those 6 months and younger
Children younger than 2 years old with chronic lung disease or congenital heart disease
Children with suppressed immune systems
Children who have neuromuscular disorders, including those who have difficulty swallowing or clearing mucus secretions

Infants and young children with RSV infection may have rhinorrhea and a decrease in appetite before any other symptoms appear. Cough usually develops one to three days later. Soon after the cough develops, sneezing, fever, and wheezing may occur. In very young infants, irritability, decreased activity, and/or apnea may be the only symptoms of infection.

Most otherwise healthy infants and young children who are infected with RSV do not need hospitalization. Those who are hospitalized may require oxygen, intubation, and/or mechanical ventilation. Most improve with supportive care and are discharged in a few days.

In Older Adults and Adults with Chronic Medical Conditions

Adults who get infected with RSV usually have mild or no symptoms. Symptoms are usually consistent with an upper respiratory tract infection which can include rhinorrhea, pharyngitis, cough, headache, fatigue, and fever. Disease usually lasts less than five days.

Some adults, however, may have more severe symptoms consistent with a lower respiratory tract infection, such as pneumonia. Those at high risk for severe illness from RSV include:

Older adults, especially those 65 years and older
Adults with chronic lung or heart disease
Adults with weakened immune systems

RSV can sometimes also lead to exacerbation of serious conditions such as:

Asthma
Chronic obstructive pulmonary disease (COPD)
Congestive heart failure

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. Consult your laboratorian for information on what type of respiratory specimen is most appropriate to use.

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 providers should consult experienced laboratorians for more information on interpretation of results.

For Older Children, Adolescents, and Adults

Healthcare providers 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 providers 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 starts in the fall and peaks in the winter in most locations in the United States.

For the latest palivizumab guidance, please consult the AAP policy statement. An accompanying AAP technical report provides additional context and rationale for the guidance. Interim guidance addressing the disruption in typical RSV seasonal patterns during the pandemic has also been provided: Updated Guidance: Use of Palivizumab Prophylaxis to Prevent Hospitalization From Severe Respiratory Syncytial Virus Infection During the 2022-2023 RSV Season (aap.org)