Respiratory syncytial virus (RSV) is an enveloped, non segmented, negative‑sense RNA virus in the genus Orthopneumovirus (family Pneumoviridae) that causes lower respiratory tract infections, particularly in infants and young children.
Virology & Pathogenesis
RSV is a member of the family Pneumoviridae (formerly subfamily Pneumovirinae) within the order Mononegavirales. As a paramyxovirus, it is an enveloped, single‑stranded negative‑sense RNA virus. The ~15 kb genome encodes non‑segmented genes for nucleocapsid (N), phosphoprotein (P), matrix (M), small hydrophobic (SH), attachment glycoprotein (G), fusion (F), transcription factor (M2) and large polymerase (L) proteins. There are two antigenic subgroups, A and B, defined by variability in the G protein. The G protein mediates attachment to heparan sulfate and CX3CR1, whereas the F protein drives fusion of viral and host membranes; F also triggers cell-to-cell fusion, forming multinucleated syncytia, a hallmark of RSV infection. Replication occurs in the cytoplasm; virions bud from the apical surface of ciliated epithelial cells. RSV interferes with type I interferon signalling and downregulates innate immunity, contributing to reinfections.
Clinical significance and epidemiology
RSV is a leading cause of respiratory illness in infants and young children. Worldwide, it is responsible for an estimated 33 million lower respiratory infections and about 200000 paediatric deaths each year. Nearly all children experience at least one RSV infection by two years of age, and reinfections occur throughout life because immunity is incomplete. The virus spreads via respiratory droplets and direct contact; peak incidence occurs in winter. Clinical manifestations range from mild cold‑like symptoms to severe bronchiolitis and pneumonia. High‑risk groups include premature infants, those with chronic lung or heart disease, the elderly and immunocompromised individuals. Management is mainly supportive, with supplemental oxygen and hydration; in severe cases mechanical ventilation may be required. Prevention strategies include palivizumab, a monoclonal antibody administered to high‑risk infants, and several F‑protein–based vaccines recently approved or under development. Respiratory syncytial virus continues to exert a substantial global burden in paediatrics and geriatrics. Improved vaccines and therapeutics are expected to reduce morbidity and mortality in vulnerable populations. Related Terms: Pneumoviridae, Bronchiolitis, Syncytium, Orthopneumovirus, Palivizumab