RSV is an infection that causes inflammation of the small airways in the lungs. It usually causes mild cold-like symptoms but can cause a serious lung infection in young children and infants called bronchiolitis.

Most children become infected with the virus by the age of 2 to 3 years old. Although all individuals can be infected with RSV, those at high risk include premature infants, young children, the elderly, immunocompromised, and children under age 2 with chronic lung conditions. The virus is most common in fall, winter, and early spring.