Overview

During the respiratory syncytial virus (RSV) season, health care providers should take into account the possibility of RSV in patients with respiratory issues. RSV is a common cause of childhood illness and leads to annual outbreaks of respiratory illnesses in individuals of all ages. While the RSV season usually begins in the fall and peaks in the winter in most areas of the United States, its severity and timing can differ each year depending on the community. Scientists are creating vaccines, monoclonal antibodies, and antiviral remedies to safeguard infants, young kids, pregnant people and older adults from severe RSV infection.

Clinical Description and Diagnosis

Infants and Young Children

RSV infection can result in various respiratory illnesses among infants and young children, such as bronchiolitis and pneumonia, but it most commonly leads to a cold-like illness. Hospitalization may be necessary for about 1-2% of children who are below six months of age with RSV infection, especially very young infants who have a higher risk of severe disease. Children with underlying conditions such as chronic lung disease, congenital heart disease, neuromuscular disorders, suppressed immune systems, and those under six months of age are considered high-risk. Rhinorrhea and decreased appetite may be the early signs of RSV infection, followed by cough, sneezing, fever, and wheezing. Irritability, decreased activity, and/or apnea could be the only symptoms of infection in very young infants. Infants and young children with otherwise good health usually improve within a few days with supportive care and do not need hospitalization. However, if hospitalized, they may need oxygen, intubation, and/or mechanical ventilation.

Older Adults and Adults With Chronic Medical Conditions

Adults who get RSV infection often have mild or no symptoms like an upper respiratory infection, while others may have lower respiratory tract infections, such as pneumonia, regardless of their level of health. Older adults over 65 years of age, adults with weakened immune systems or who have chronic lung disease or heart disease are more susceptible to severe RSV illness. Furthermore, RSV can worsen underlying health conditions such as asthma, COPD, and congestive heart failure.

RSV Testing

RSV symptoms in patients are not specific and can be similar to other viral respiratory infections and certain bacterial infections. Multiple laboratory tests are available that can verify the presence of RSV infection. These tests can be conducted on respiratory samples obtained from the upper and lower respiratory tracts.

The following are the most widely used RSV clinical laboratory tests:

Real-time reverse transcriptase-polymerase chain reaction (rRT-PCR), which provides higher sensitivity than antigen testing and culture
Antigen testing, which is highly sensitive in children but may not be sensitive in adults

Less commonly used tests include:

Viral culture
Serology, usually only utilized for surveillance and research studies

Although some tests can differentiate between RSV subtypes A and B, the clinical significance of these subtypes is uncertain. Laboratory technologists may determine which respiratory specimen sample is adequate and appropriate for use.

Testing Infants and Young Children

Both rRT-PCR and antigen detection tests are reliable techniques for detecting RSV infection in infants and young children. In this age group, the RSV sensitivity of antigen detection tests normally falls between 80% to 90%. Healthcare practitioners should seek the expertise of knowledgeable laboratory specialists for further guidance on interpreting test results.

Testing Older Children, Adolescents, and Adults

When evaluating older children and adults for RSV, health care providers should employ rRT-PCR assays that are extremely sensitive. Commercial rRT-PCR assays for RSV are now easily accessible. Typically, these assays’ sensitivity is superior to that of virus isolation and antigen detection techniques. Because older children and adults may have lower viral loads in their upper respiratory tract, antigen tests are not sensitive enough for detecting the virus in this group. It is crucial to seek guidance from experienced laboratory professionals for accurate test result interpretation.

Prophylaxis and High-Risk Infants and Young Children

(AAP) for high-risk infants and young children who may benefit from immunoprophylaxis based on various medical conditions and gestational age. Typically, it is given via monthly intramuscular injections during the RSV season, which starts in the autumn and reaches its pinnacle during the winter in most parts of the United States. For the most up-to-date palivizumab guidance, the AAP policy statement should be consulted. The AAP technical report, providing further rationale and context for the guidance, is also available. Additionally, interim guidelines have been provided to address disruptions in typical RSV seasonal patterns during the pandemic: Updated Guidance: Use of Palivizumab Prophylaxis to Prevent Hospitalization From Severe Respiratory Syncytial Virus Infection During the 2022-2023 RSV Season (aap.org).³

RSV Vaccines

In May 2023, both Arexvy (GSK) and Abrysvo (Pfizer) RSV vaccines were authorized for use in the United States.^4,5 Studies to develop an RSV vaccine have been ongoing for several decades, with one published in 2013 leading to the creation of the approved vaccines. This work also paved the way for the rapid development of COVID-19 vaccines. Additionally, other vaccines are being developed, such as those designed for pregnant women to provide passive immunity to their infant through maternal antibodies, as well as vaccines for children.