RSV commonly causes infection in childhood. It is highly infectious and almost all babies get it before the age of 2. Many babies (and most older children) get only a slight cold from RSV; however, some babies with RSV develop potentially serious lower respiratory infections such as bronchiolitis (infection of the small breathing tubes in the lungs) and pneumonia (lung infection). These infections are especially dangerous in babies who were born prematurely, have lung or heart problems or certain other chronic illnesses. Your baby can get RSV at any time of year, but it is most common from fall to spring. Contact you health care provider if you have questions.