Respiratory syncytial virus (RSV) infection is a common illness that affects people throughout life. The first infection is usually the worst and occurs in early childhood. About 90 out of 100 children have had at least one RSV infection by age 2.¹

RSV infection spreads easily where there are many people in one area, such as households, urban areas, nursing homes, and child care centers. Because symptoms often resemble those of the common cold, RSV infection is often not recognized. But in the United States, this virus is the most common cause of respiratory infection in young children that requires hospitalization.

Bronchiolitis is the major complication of RSV in infants. In the United States, about 24 out of 1,000 infants (younger than 1 year of age) are hospitalized for bronchiolitis caused by RSV.² Certain populations are affected differently. For example, about 29 out of 1,000 American Indian and Alaska Native infants who receive health care through the Indian Health Services are hospitalized because of RSV bronchiolitis infection.².

An RSV infection is more likely to cause serious complications in infants younger than 6 months of age, especially those who were born prematurely or have another health problem. Other people who have an increased risk of developing complications include adults age 65 and older and anyone with chronic health problems, especially heart disease, lung disease, or immune system problems. In older people, pneumonia is a common complication of RSV.