Respiratory Syncytial Virus (RSV) is a widespread respiratory virus that can lead to infections in the lungs and breathing passages. While many experience mild symptoms, some individuals face severe illness, necessitating medical interventions. Understanding the available medical options, including antiviral drugs and preventative treatments, is important for protecting at-risk populations.
Key Facts About RSV
RSV is a common cause of respiratory infections, affecting nearly all children by the age of two. The virus primarily infects cells lining the respiratory tract, from the nose down to the lungs. Symptoms appear four to six days after exposure and often resemble a common cold, including a runny or congested nose, sore throat, dry cough, low-grade fever, sneezing, and headache.
For most healthy adults and older children, RSV results in mild symptoms, with recovery usually occurring within a week. However, RSV can progress to more severe lower respiratory tract infections like bronchiolitis, which is inflammation of the small airways, or pneumonia. This can be dangerous for infants under six months, very premature babies, older adults, and individuals with chronic heart or lung conditions or weakened immune systems.
RSV spreads easily through infectious respiratory droplets released when an infected person coughs or sneezes. It can also transmit through direct contact with an infected individual or by touching contaminated surfaces, then touching one’s eyes, nose, or mouth. People are contagious for 3 to 8 days, even before symptoms appear. Some infants and immunocompromised individuals can spread the virus for up to four weeks or longer.
Antiviral Drug Treatment for RSV
Ribavirin is an antiviral drug used to treat severe RSV infections. This medication works by inhibiting the synthesis of viral DNA and RNA, preventing the virus from replicating.
Ribavirin is administered as an aerosolized mist through a special nebulizer, usually in a hospital setting. Its use is highly restricted due to its side effect profile and administration challenges. Side effects can include breathing problems, chest pain, fever, bluish discoloration of the lips or nail beds, seizures, unusual blood pressure or heart rate, and hemolytic anemia. It is also contraindicated in pregnant women due to potential harm to the fetus.
Due to these factors, Ribavirin is reserved for very specific, severe cases of RSV, primarily in high-risk patients. These include hospitalized infants and young children with severe lower respiratory tract infections, particularly those who are immunocompromised or have severe underlying lung disease. Treatment is most effective when initiated early in the course of severe infection.
Preventative Monoclonal Antibodies for RSV
Monoclonal antibodies offer a different approach to managing RSV, providing passive immunity rather than directly inhibiting viral replication like antivirals. These laboratory-produced proteins mimic the body’s natural antibodies, offering immediate, temporary protection against the virus.
One such monoclonal antibody is Palivizumab, known by the brand name Synagis. It works by binding to the RSV fusion (F) protein, which is essential for the virus to enter host cells, blocking viral replication. Palivizumab is given as a monthly intramuscular injection throughout the RSV season. It has been shown to reduce hospitalizations due to RSV infection in high-risk infants by approximately 56% to 65%.
Another advancement is Nirsevimab, marketed as Beyfortus. This long-acting monoclonal antibody also targets the RSV prefusion F protein, interfering with cellular membrane fusion and preventing viral entry. Nirsevimab provides extended protection for at least five months with a single intramuscular injection. Studies have shown Nirsevimab can reduce the risk of medically attended RSV lower respiratory tract infections by approximately 70-75% and hospitalizations by 98% in treated infants.
Both Palivizumab and Nirsevimab have favorable safety profiles, with common side effects including injection site reactions and fever. Serious hypersensitivity reactions, including anaphylaxis, have been reported, so caution is advised for infants with bleeding disorders. These preventative antibodies are administered to specific high-risk infant populations to prevent severe RSV disease rather than to treat an active infection.
Who Receives RSV Medications and When
The administration of RSV medications, whether antiviral or preventative, is highly specific to patient populations and timing. Ribavirin, the antiviral drug, is reserved for hospitalized infants and young children experiencing severe lower respiratory tract infections due to RSV, particularly those who are immunocompromised. Treatment with Ribavirin is initiated within the first 24 hours of diagnosis in these high-risk, severely ill patients.
Preventative monoclonal antibodies, Palivizumab and Nirsevimab, are administered to protect vulnerable infants from severe RSV disease before or during the RSV season. Palivizumab is given as a series of monthly injections for five months during the RSV season to specific high-risk infants, including premature infants born at or before 35 weeks of gestation, and children under two years of age with chronic lung disease of prematurity or hemodynamically significant congenital heart disease.
Nirsevimab offers single-dose protection for an entire RSV season. It is recommended for all infants under eight months of age who are born during or entering their first RSV season. This can be administered shortly before or during the RSV season, ideally within one week of birth for infants born during the season.
Nirsevimab is also recommended for children aged 8 to 19 months who remain at increased risk for severe RSV disease and are entering their second RSV season. This includes children with chronic lung disease of prematurity requiring medical support, severely immunocompromised children, and some American Indian or Alaska Native children who experience higher rates of severe RSV disease. If an infant received Palivizumab in their first season and is eligible for protection in their second season, Nirsevimab is recommended.