Question
Respiratory Syncytial virus.
Answer
Respiratory Syncytial Virus (RSV): an enveloped, single-stranded, negative-sense RNA virus, belonging to the Pneumoviridae family (genus Orthopneumovirus).
Clinical significance: the most common cause of bronchiolitis and severe lower respiratory tract infection in infants and young children worldwide, and a significant cause of morbidity in the elderly and immunocompromised. Presents with fever, cough, wheeze, and respiratory distress; in infants, can cause significant hypoxia requiring hospitalization. Named for the characteristic cytopathic effect (syncytium formation — multinucleated giant cells) it produces in infected cell culture.
Transmission: via respiratory droplets and direct/fomite contact; highly contagious, with seasonal (winter) epidemics in temperate climates.
Laboratory diagnosis:
- Rapid antigen detection test (immunochromatographic) — on nasopharyngeal aspirate/swab, widely used for rapid point-of-care diagnosis.
- RT-PCR — the most sensitive method, often included in multiplex respiratory viral panels.
- Direct Fluorescent Antibody (DFA) test — on nasopharyngeal secretions.
- Virus isolation in cell culture — demonstrating characteristic syncytial cytopathic effect, though slower and not routinely used for clinical diagnosis.
Prevention: Palivizumab — a monoclonal antibody providing passive immunoprophylaxis, given to high-risk infants (e.g., premature infants, those with chronic lung/cardiac disease) during the RSV season; newer maternal and infant RSV vaccines/monoclonal antibody products have also been developed to reduce severe RSV disease burden in infants.