respiratory syncytial virus

Respiratory syncytial virus, almost always shortened to RSV, is so common that nearly every child catches it by the age of two. In most older children and adults it causes nothing worse than a cold, but in tiny babies and frail older people it can swell the smallest airways and the lungs themselves, turning an ordinary winter bug into a serious illness.

RSV is a respiratory virus that spreads in seasonal winter outbreaks through droplets and contact. Its name comes from the way infected cells fuse together into clumps called syncytia. In infants its signature illness is bronchiolitis — inflammation of the smallest airways — causing wheeze, fast labored breathing and feeding difficulty; in the very young, the elderly and the immunocompromised it can progress to pneumonia.

Most cases are managed with supportive care: keeping the child hydrated, clearing the nose, and giving oxygen if levels fall; antibiotics do not help a viral infection. Severe cases, especially in premature or heart-affected infants, may need hospital oxygen or breathing support. Preventive options have grown, including a long-acting antibody for high-risk infants and vaccines for older adults and during pregnancy.

Because RSV looks much like other respiratory viruses early on, it is often confirmed by a nasal swab test mainly when the result will change care, such as for an admitted infant, rather than in every mild case.