Respiratory Syncytial Virus (RSV) is a respiratory virus that infects the lungs and breathing passages. RSV is the primary cause of bronchiolitis and pneumonia in children under the age of one.
It is very common, and almost all children have had RSV before they have reached the age of two. RSV can also attack adults of any age. Recently, RSV has been recognized as a significant problem in certain adult populations. These include the elderly, persons with cardiopulmonary diseases, and immunocompromised individuals.