Respiratory Syncytial Virus (RSV)

  • Medical Author:
    John Mersch, MD, FAAP

    Dr. Mersch received his Bachelor of Arts degree from the University of California, San Diego, and prior to entering the University Of Southern California School Of Medicine, was a graduate student (attaining PhD candidate status) in Experimental Pathology at USC. He attended internship and residency at Children's Hospital Los Angeles.

  • Medical Editor: Mary D. Nettleman, MD, MS, MACP
    Mary D. Nettleman, MD, MS, MACP

    Mary D. Nettleman, MD, MS, MACP

    Mary D. Nettleman, MD, MS, MACP is the Chair of the Department of Medicine at Michigan State University. She is a graduate of Vanderbilt Medical School, and completed her residency in Internal Medicine and a fellowship in Infectious Diseases at Indiana University.

Respiratory syncytial virus (RSV) infection facts

  • RSV is a highly contagious virus infection that most commonly causes illness during the winter season.
  • Most children who develop an RSV infection have mild symptoms of fever, nasal congestion, and nasal discharge.
  • High-risk groups are more likely to have a more severe disease process, including wheezing (bronchiolitis in infants) and/or pneumonia. Such high-risk groups include premature infants, those children with a compromised immune system, or those with chronic pulmonary disease or congenital/acquired cardiac disease.
  • Supportive care is the mainstay of therapy. For high-risk patients, palivizumab (Synagis) preventative therapy is available.

What is the respiratory syncytial virus (RSV)?

The respiratory syncytial virus (RSV), discovered in 1956, is capable of causing a broad spectrum of illnesses. Older children and adults will commonly experience a "bad cold" lasting one to two weeks. Fever, nasal congestion, and cough are their most common complaints. However, in babies and toddlers, RSV can produce severe pulmonary diseases, including bronchiolitis (inflammation of the terminal airways which produces wheezing) and pneumonia (infection of these terminal airways).

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Respiratory Syncytial Virus (RSV)

Is RSV Contagious?

Respiratory syncytial virus (RSV) is contagious. In the United States, it's the most common cause of inflammation of the small airways in the lungs (bronchiolitis) and of pneumonia in children under 1 year of age. It also is significant cause of respiratory illnesses in older adults. Nearly all children in the U.S. will have been infected by RSV by 2 years of age. RSV usually causes a mild respiratory infection, but it can occasionally cause more serious infections that require hospitalization from breathing compromise with bronchiolitis or pneumonia.

When does RSV infection occur, and who gets it?

Infection with RSV is seasonal. In temperate climates, RSV infections usually occur during the late fall, winter, or early spring months. Annual community outbreaks of RSV infection often last four to five months. The winter season (November through April) tend to be most likely to experience RSV epidemic disease. For unknown reasons, severity of illness and frequency of disease often alternate on an annual basis. For example: a "bad" year (large number of patients with moderately severe disease) is followed by a "good" year (fewer number of patients with less severe disease).

More than half of all infants are exposed to RSV by their first birthday. Many have few or mild symptoms. However, some babies with RSV become very ill. RSV is the most common cause of bronchiolitis and pneumonia among infants and children under 1 year of age.

After childhood, RSV causes repeated infections throughout life. These infections are usually associated with cold-like symptoms. However, severe lower respiratory tract disease (for example, wheezing and/or pneumonia) may occur at any age, especially among the elderly or among those with compromised cardiac, pulmonary, or immune systems.

Who is at risk for severe disease?

Several broad categories of patients are most vulnerable to RSV infection. These include:

  • (a) premature infants and all infants less than 1 year of age,
  • (b) children 2 years old with cardiac disease or chronic lung disease (for example, asthma, cystic fibrosis, etc.),
  • (c) those of any age with a compromised immune system, and
  • (d) those 65 years of age or older.

Is RSV infection contagious, and how is RSV infection transmitted?

RSV disease is very highly contagious. Annually 100,000-120,000 babies less than 1 year old require hospitalization. The RSV incubation period (time between exposure and development of symptoms) is two to eight days. It is spread via respiratory secretions through close contact with infected people or contact with contaminated surfaces or objects. Infection can occur when infectious particles contacts mucous membranes of the eyes, mouth, or nose, and possibly through the inhalation of droplets generated by a sneeze or cough. Those who develop RSV are contagious during the first three to eight days of their illness.

What are the symptoms of RSV infection?

  • The symptoms in most infants are similar to those of a bad cold. These include fever, prominent runny nose, and nasal congestion.
  • The duration of these symptoms is one to two weeks. During their first RSV infection, some babies and young children also have signs and symptoms of bronchiolitis or pneumonia.
  • Bronchiolitis is a clinical state of infants (by definition) during which inflammation of the terminal airways restricts airflow and may produce wheezing.
  • The majority of children hospitalized for RSV infection are under 6 months of age. The need for supplemental oxygen, IV fluids, and pulmonary inhalation therapy are the most common indicators for hospitalization.
    • If wheezing causes an infant's respiratory rate to increase substantially, they may have a difficult time taking in adequate fluids and become dehydrated.

Following childhood, RSV may cause repeated infections with moderate-to-severe cold-like symptoms although severe lower respiratory tract disease (pneumonia and/or wheezing) may occur with RSV at any age.

How is RSV infection diagnosed?

The diagnosis of RSV infection can be made by a number of different laboratory tests, including

  • isolation of the virus, detection of viral antigens,
  • detection of viral RNA,
  • demonstration of a rise in serum antibodies, or
  • a combination of these approaches.

Most clinical laboratories today use nasal swab tests based on antigen detection to diagnose RSV infection. This technique is 80%-90% reliable. A newer test protocol (RT-PCR) is more reliable and is replacing the antigen-detecting test in many hospitals and community laboratories.

What is the treatment for an RSV infection?

For children with mild RSV disease, no specific treatment is necessary other than the treatment of symptoms (such as acetaminophen [Tylenol] to reduce fever).

Children with more severe disease may require oxygen therapy and sometimes mechanical ventilation. Ribavirin aerosol (Virazole) may be used in the treatment of some patients with severe disease. Some investigators have used a combination of intravenous immune globulin (IVIG) with high titers of neutralizing RSV antibody (RSV-IVIG) and ribavirin to treat patients with compromised immune systems.

How can RSV infection be prevented?

Frequent hand washing and not sharing items such as cups, glasses, and utensils with people who have RSV illness should decrease the spread of virus to others.

Excluding children with colds or other respiratory illnesses (without fever) who are well enough to attend child care or school settings will probably not decrease the transmission of RSV, since it is often spread in the early stages of illness prior to the development of more severe symptoms.

In a hospital setting, RSV transmission can and should be prevented by strict attention to contact precautions, such as hand washing and wearing gowns and gloves.

In 1998, a new product called palivizumab (Synagis) was licensed to help prevent severe RSV disease in certain high-risk infants with predisposing factors such as moderate/severe prematurity, chronic lung disease, congenital heart disease, etc. Palivizumab is not a treatment for RSV but rather a tool to help prevent RSV infection. Those receiving Synagis receive a monthly injection during the RSV season. Synagis is quite expensive, and insurance companies often have strict guidelines limiting those for whom they will pay this medication.

Is there an RSV vaccine?

Unfortunately, there is no RSV vaccine yet, although development of one is a high research priority.

Effective immunity against RSV requires a continuous solid level of antibodies against the virus. There is particular concern for RSV in premature babies because of their lack of maturity and lack of protective antibodies. There is a similar concern about RSV in people of all ages with immunodeficiency. Most people's immune system loses its protective capability a few months following exposure to RSV. This enables individuals to experience repeated episodes of illness during each RSV season.

What is the prognosis of an RSV infection?

Most babies and toddlers tolerate an RSV infection well. Unless they require supplemental oxygen or are at risk for dehydration, they can receive any necessary respiratory support from their parents in their home. Children commonly respond to inhaled bronchodilators to help control wheezing. The development of portable nebulizers has made such therapy available for home use. Unfortunately, no current vaccination is available to prevent RSV infection. Hopefully, current research in this area will soon be successful.

Medically reviewed by Robert Cox, MD; American Board of Internal Medicine with subspecialty in Infectious Disease


United States. Centers for Disease Control and Prevention. "Respiratory Syncytial Virus Infection (RSV)." Mar. 31, 2010. <>.

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