Respiratory Syncytial Virus (RSV)

Respiratory Syncytial Virus (RSV) is an RNA virus that is transmitted primarily by respiratory droplets when a person coughs or sneezes. It can also be transmitted through direct contact with a contaminated surface. 

RSV was originally called the chimpanzee corzya virus because it was first isolated from a chimpanzee with rhinorrhea. Its name was changed to RSV when scientists discovered that it caused infected epithelial cells to fuse together and form giant cells known as syncytia. 

In the United States, the annual RSV season usually starts in the fall and peaks during the winter. Hawaii and Florida experience RSV infections year-round.  Because natural infection with RSV provides limited protective immunity, RSV causes repeated symptomatic infections throughout life. 

RSV is the most common cause of bronchiolitis and pneumonia in young children and is the number one cause of hospitalizations in children under the age of 1 in the United States. Children of any age with underlying cardiac or pulmonary disease or who are immunocompromised are at risk for serious complications from this virus. CDC estimates that every year RSV causes between 58,000 and 80,000 hospitalizations and 100 to 300 deaths in children under the age of 5 years.

In adults, RSV usually causes upper respiratory tract manifestations but may cause lower respiratory tract disease, especially in the elderly and in immunocompromised persons. Most patients recover in one to two weeks, but infection in immunocompromised persons can be associated with high death rates. RSV kills more adults in the United States than children. CDC estimates that every year RSV causes between 60,000 and 160,000 hospitalizations and 6,000 to 10,000 deaths among adults ages 65 years and older.

RSV is a common, but preventable, cause of nosocomial infection, especially during community outbreaks. Sources for nosocomial infection include infected patients, staff, visitors, or contaminated surfaces. 

Nirsevimab is a long-acting monoclonal antibody approved by the Food and Drug Administration (FDA) in 2023 to protect infants and some young children at increased risk for severe RSV disease. One dose of nirsevimab administered as an intramuscular injection protects infants for at least 5 months.

RSVPreF3 and RSVpreF are recombinant protein vaccines that were both approved by FDA in 2023 for use in adults ages 60 years and older to prevent RSV-associated lower respiratory tract disease. Each vaccine is more than 80% efficacious in preventing RSV-associated lower respiratory tract disease.

In 2023, FDA also approved the RSVpreF vaccine (AbrysvoTM, Pfizer) for use in pregnant people during weeks 32 through 36 of gestation for the prevention of RSV-associated lower respiratory tract disease in infants from birth through 6 months of age.

Ribavirin therapy may be considered for patients who are seriously ill or who are at high risk for severe complications of the infection.

RSV can be detected by viral culture, rapid antigen testing, or multiplex respiratory pathogen panels. Roche Cobas Liat can simultaneously test for Influenza A and B and RSV. Cepheid GeneXpert platform can simultaneously test for Influenza, RSV, and SARS-CoV-2. Cultures require 3 to 14 days’ incubation before cytopathic effects are seen. The sensitivity of cultures is often impaired by the lability of the virus during specimen transport to the laboratory.  Rapid antigen testing for RSV overcomes this limitation and is much quicker to perform.  Comparisons with culture have shown the rapid antigen test to be very sensitive and specific. RSV antigen results are reported as negative or positive.  Reference value is a negative result.

Adequate specimen collection is crucial to achieve accurate test results.  A nasopharyngeal aspirate should be obtained. Nasal swabs are not adequate for RSV testing and may cause false negative results. An equivocal or negative test does not eliminate the possibility of RSV infection, because inadequate collection, improper handling, or low-level virus shedding may cause them.

Reference

CDC Health Alert Network, Increased Respiratory Syncytial Virus (RSV) Activity in Parts of the Southeastern United States: New Prevention Tools Available to Protect Patients, HAN00498, Sep 5, 2023.