Learn About Respiratory Syncytial Virus (RSV) | American Lung Association

Learn About Respiratory Syncytial Virus (RSV)

Respiratory syncytial virus (RSV) is a common respiratory virus that can affect people of all ages. In older children and adults, it causes mostly upper respiratory symptoms (colds), but it can cause a serious infection in the lungs (bronchiolitis or pneumonia) among infants and adults with serious underlying medical problems.

Key Facts

  • RSV will infect almost all children during the first 2 years of age, although most cases will have only minor symptoms.
  • RSV-related infections in children younger than 5 years of age account for more than 2 million visits to the doctor or to the emergency department each year.
  • It is a leading cause for hospitalization for infants younger than 1 year of age.

What Is RSV?

RSV is a virus transmitted only between humans. There are two different strains (A and B) that may cause differences in the severity of the illness. RSV is spread through infected droplets from secretions of the mouth or nose. RSV can survive for at least 30 minutes on hands and for several hours on infected surfaces. Every year, RSV causes epidemics. These usually occur during the winter and early spring. However, the actual timing and the duration vary between regions.

How RSV Affects Your Body

RSV can affect any part of the respiratory tract causing intense inflammation.

  • The infection is most serious when it affects the small breathing tubes (bronchioles) causing (bronchiolitis).
  • It can also cause infection in the rest of the lungs (pneumonia).

How Serious Is RSV?

Most people (including infants) usually develop only mild disease similar to that of a common cold, with congestion, runny nose, and cough. About 25 percent to 40 percent of the affected infants and children will develop symptoms of bronchiolitis or pneumonia, and 5 percent to 20 percent will require hospitalization. Children with RSV who require hospitalization, and especially those who need admission to the pediatric intensive care unit (PICU), are usually younger than 6 months of age. The elderly and adults with chronic heart or lung disease or with weakened immune systems are at high risk for developing severe RSV disease if they are reinfected. Because people do not form long-lasting immunity to RSV, they can become infected repeatedly over their lifetime.


    This content was developed in partnership with the CHEST Foundation, the philanthropic arm of the American College of Chest Physicians.


    Ask An Expert

    Questions about your lung health? Need help finding healthcare? Call 1-800-LUNGUSA.

    Get help
    We need your generous support

    Make a difference by delivering research, education and advocacy to those impacted by lung disease.

    What is LUNG FORCE?

    LUNG FORCE unites women and their loved ones across the country to stand together in the fight against lung cancer.

    Get involved
    Join the fight for healthy lungs and healthy air.
    Donate Now.