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The respiratory syncytial virus (RSV) is the major cause of infections of the breathing passages and lungs in infants and young children. In addition to causing pneumonia, it is the leading cause of bronchiolitis (an infection of the bronchioles, the small breathing tubes of the lungs). Some cases of bronchiolitis, however, are caused by the flu, parainfluenza virus, adenovirus, or measles.

Respiratory syncytial virus is transmitted from an infected child by secretions from the nose or mouth by direct contact or airborne droplets. The period of greatest contagiousness is in the first 2 to 4 days of the infection. The incubation period ranges from 2 to 8 days, commonly 4 to 6 days. Annual epidemics take place during the winter and early spring.

Signs and Symptoms

Many children with RSV infections have only mild symptoms, typically similar to the symptoms of a common cold. In children younger than 2 years, the infection may progress to symptoms more commonly found in bronchiolitis.

  • Initially, the child will have a runny nose, mild cough, and in some cases, a fever.
  • Within 1 to 2 days, the cough will get worse.
  • At the same time, the youngster’s breathing will become more rapid and difficult. He may wheeze each time he breathes out.
  • Your child will have a hard time drinking because he is using so much energy breathing. Even swallowing becomes very difficult for these youngsters.
  • His fingertips and the area around his lips may turn a bluish color, a sign that his strained breathing is not delivering enough oxygen to his bloodstream.

What You Can Do

In the early stages of an RSV infection, help ease your child’s cold-like symptoms. Gentle suctioning of the nose may be useful to clear the nostrils.

Mist has not been shown to be useful. Hot-air vaporizers should be avoided because of the risk for scald burns, and cool-mist vaporizers are often contaminated with molds. Make sure your child drinks enough liquid to prevent dehydration.

When to Call Your Pediatrician

Contact your pediatrician immediately if your baby or child

  • Has breathing difficulties
  • Is younger than 2 or 3 months and has a fever
  • Shows signs of dehydration, such as a dry mouth, crying without tears, and urinating less often

How Is the Diagnosis Made?

Your pediatrician may order laboratory tests of specimens taken from your child’s nose and throat to see if RSV is present. The virus can be grown in special cultures, or parts of the virus can be identified by rapid tests.


If your child is having difficulty breathing or has asthma or a tendency for reactive airways, your doctor may try a medicine called a bronchodilator to help open his airways. Bronchodilators won’t help many infants with this viral infection. Some youngsters with bronchiolitis may have to be hospitalized for treatment with oxygen. If your child is unable to drink because of rapid breathing, he may need to receive intravenous fluids. On rare occasions, infected babies will need a respirator to help them breathe.

Antibacterials are not used for treating viral infections, including those caused by RSV.

What Is the Prognosis?

Most children with RSV infections are well on their way to recovery in about a week, and almost all fully recover. Nearly all children are infected with RSV at least once by 2 years of age, and a recurrence of the infection throughout life is common. As the child grows, RSV infections become less serious than when they were infants and are usually hard to distinguish from a cold.

These infections can make asthma and other chronic breathing conditions worse. Infants with congenital heart disease may have a more severe case of RSV. Some children will require hospitalization, and a few will need intensive care.


Your child should avoid close contact with other children and adults who are infected with RSV or other viruses that cause bronchiolitis. In child care centers, good hygiene practices should be used by the staff and the youngsters, including frequent and thorough hand washing.

Vaccines are being developed for RSV, but none are currently licensed for use. Palivizumab is an antibody that has been made to prevent RSV infection.

It is given as an intramuscular shot once a month to children who are at increased risk for serious diseases caused by RSV. These include premature babies, babies with chronic lung disease, and some babies with immunodeficiencies.


Last Updated
Immunizations & Infectious Diseases: An Informed Parent's Guide (Copyright © 2006 American Academy of Pediatrics)
The information contained on this Web site should not be used as a substitute for the medical care and advice of your pediatrician. There may be variations in treatment that your pediatrician may recommend based on individual facts and circumstances.