RSV is an enveloped virus of the Pneumoviridae family containing two serotypes: RSV-A and RSV-B. It has a negative-sense, single-stranded RNA genome (approximately 15.2 kb) comprising 10 genes that encode 11 proteins. RSV primarily infects ciliated respiratory epithelial cells in the respiratory tract. Once infection is established in the upper airways, the virus can spread to the lower respiratory tract, where it induces significant inflammation.
Transmission occurs via respiratory droplets, direct contact, or fomite transmission from contaminated surfaces. Seasonal outbreaks are common in temperate regions of the Northern and Southern Hemispheres, with infections peaking during the winter months. In equatorial regions, RSV circulates year-round.
Symptoms of RSV infection are typically mild and cold-like in healthy individuals. These may include cough, nasal congestion, sneezing, but rarely fever. In severe cases, such as pneumonia or bronchiolitis, symptoms may progress to include worsening cough, shortness of breath, wheezing and respiratory failure.
There is no specific treatment for RSV infection. Most cases resolve over time (within one or two weeks) without medical intervention. Severe infections may require hospitalization, with supportive treatment including fluids to prevent dehydration and oxygen or ventilation to assist with breathing. Antivirals such as ribavirin may be used in select cases but are generally reserved for severe illness.
Non-pharmaceutical preventive measures rely on good hygiene practices, such as regular handwashing and avoiding close contact with symptomatic individuals—particularly for those in high-risk groups.
Until recently, the only commonly used preventive agent for RSV was palivizumab (Synagis®), which had been in clinical use for over 25 years. Although effective, its high cost and need for monthly administration throughout the RSV season limited its use to the most high-risk infants in high-income countries (HICs).
With a greater understanding of the RSV fusion protein (the protein responsible for viral entry into host cells), effective vaccines and extended half-life monoclonal antibodies have now been developed. Those currently approved include:
– Older adult vaccines: for example, GSK’s Arexvy and Pfizer’s Abrysvo
– Maternal vaccines: for example, Abrysvo
– Long-acting monoclonal antibodies: for example, nirsevimab (Beyfortus from AZ and Sanofi)
Real-world data from areas of high uptake show excellent effectiveness (60-85%) in preventing severe RSV-associated disease.
