In healthy children, respiratory syncytial virus (RSV) infections tend to be mild and resemble a cold. Children who have only upper respiratory system symptoms, such as a sore throat or a runny nose, usually recover in about 10 to 14 days.

Two different types and many different subtypes (strains) of RSV exist. For this reason, you cannot have full immunity to the virus and may have many RSV infections throughout your life. A child's first RSV infection, which almost always occurs by age 2, usually is the worst. Some babies and children have an increased risk of having complications from an RSV infection because their immune system is unable to fight off the virus. In addition, babies have narrow breathing tubes that can clog easily, making breathing difficult. The most common complications for young children are bronchiolitis and pneumonia, which are lower respiratory tract infections.

Adults older than 65 have an increased risk of developing complications following infection with RSV. Pneumonia is a particular risk, especially if other health problems exist, such as chronic obstructive pulmonary disease (COPD) or heart failure.

It may take older adults longer to recover from RSV infection and its complications than other age groups.