RSV (Respiratory Syncytial Virus)

RSV (respiratory syncytial virus) is a very common respiratory virus — most children have been infected at least once by age two — that usually causes mild, cold-like illness but can be more serious in certain groups.

Symptoms in Most People

In healthy older children and adults, RSV typically causes symptoms similar to a common cold: runny nose, cough, sneezing, low-grade fever, and sore throat, usually resolving within one to two weeks.

Why It's More Serious for Some

RSV is a leading cause of bronchiolitis (inflammation of the small airways) and pneumonia in infants, particularly those born prematurely or under six months old, and can also cause serious illness in older adults and people with chronic heart or lung disease or weakened immune systems.

Warning Signs in Infants

Watch for fast or labored breathing, wheezing, flaring nostrils, a visible pulling-in of the chest with each breath, poor feeding, or unusual lethargy — these need prompt medical evaluation rather than waiting to see if it passes.

Treatment and Prevention

Most cases are managed with supportive care — fluids, rest, and fever control — since there's no specific antiviral treatment for routine cases. RSV vaccines and preventive antibody treatments are now available for certain high-risk infants and older adults; ask a doctor whether these apply to your situation.