Respiratory Syncytial Virus (RSV)

Clinical Description

In Infants

RSV infection can cause a variety of respiratory illnesses, some of which may cause fever. RSV infection most commonly causes a cold-like illness, but it can also cause bronchitis, croup, and lower respiratory infections like bronchiolitis and pneumonia. Of every 100 infants and young children with RSV infection, 25 to 40 (25% to 40%) will show signs of pneumonia or bronchiolitis. Premature infants, very young infants, and those with chronic (always present) lung or heart disease or with suppressed (weakened) immune systems have a greater chance of having a more severe infection (such as a lower respiratory tract infection). Infection without symptoms is rare among infants.

Infants with a lower respiratory tract infection typically have a runny nose and a decrease in appetite before any other symptoms appear. Cough usually develops 1 to 3 days later. Soon after the cough develops, sneezing, fever, and wheezing may occur. In very young infants, irritability, decreased activity, and apnea may be the only symptoms of infection.

Most otherwise healthy infants who are infected with RSV do not need hospitalization. Those who are hospitalized may require oxygen, intubation, and/or mechanical ventilation. Most improve with supportive care and are discharged in a few days.

In Adults

Symptomatic RSV infections may occur in adults, particularly in healthcare workers or caretakers of small children. Disease usually lasts less than 5 days, and symptoms are usually consistent with an upper respiratory tract infection and can include a runny nose (rhinorrhea), sore throat (pharyngitis), cough, headache, fatigue, and fever, but some high-risk adults, such as those with certain chronic illnesses or immunosuppression, may have more severe symptoms consistent with a lower respiratory tract infection, such as pneumonia.


Several different types of laboratory tests are available for diagnosis of RSV infection. Rapid diagnostic assays performed on respiratory specimens are available commercially. Most clinical laboratories currently utilize antigen detection tests, and many supplement antigen testing with cell culture. Compared with culture, the sensitivity of antigen detection tests generally ranges from 80% to 90%. Antigen detection tests and culture are generally reliable in young children but less useful in older children and adults. Because of its thermolability, the sensitivity of RSV isolation in cell culture from respiratory secretions can vary among laboratories. Experienced laboratorians should be consulted for optimal results.

RT-PCR assays are now commercially available for RSV. The sensitivity of these assays often exceeds the sensitivity of virus isolation and antigen detections methods. Use of highly sensitive RT-PCR assays should be considered, particularly when testing older children and adults because they may have low viral loads in their respiratory specimens.

Serologic tests are less frequently used for routine diagnosis. Although useful for seroprevalence and epidemiologic studies, a diagnosis using paired acute- and convalescent-phase sera to demonstrate a significant rise in antibody titer to RSV cannot be made in time to guide patient care.


RSV can cause upper respiratory infections (such as colds) and lower respiratory tract infections (such as bronchiolitis and pneumonia). In children under 1 year of age, RSV is the most important cause of bronchiolitis, an inflammation of the small airways in the lung.

Almost all children will have had an RSV infection by their second birthday. When infants and children are exposed to RSV for the first time, 25% to 40% of them have signs or symptoms of bronchiolitis or pneumonia, and 0.5% to 2% will require hospitalization. Most children hospitalized for RSV infection are under 6 months of age.

Infants and children infected with RSV usually show symptoms within 4 to 6 days of infection. Most will recover in 1 to 2 weeks. However, even after recovery, very young infants and children with weakened immune systems can continue to spread the virus for 1 to 3 weeks.

People of any age can get another RSV infection, but later infections are generally less severe. The elderly and adults with chronic heart or lung disease or with immune systems weakened by medical conditions or treatments remain at high risk for developing severe RSV disease if reinfected.

In temperate climates, RSV infections generally occur during fall, winter, and early spring. The timing and severity of RSV circulation in a given community can vary from year to year.

People infected with RSV are usually contagious for 3 to 8 days. However, some infants and people with weakened immune systems can be contagious for as long as 4 weeks. RSV is often introduced into the home by school-aged children who are infected with RSV and have a mild upper respiratory tract infection, such as a cold. RSV can be rapidly transmitted to other members of the family, often infecting about 50% of other household members.

RSV can be spread when droplets containing the virus are sneezed or coughed into the air by an infected person. Such droplets can linger briefly in the air, and if someone inhales the particles or the particles contact their nose, mouth, or eye, they can become infected.

Infection can also result from direct and indirect contact with nasal or oral secretions from infected persons. Direct contact with the virus can occur, for example, by kissing the face of a child with RSV. Indirect contact can occur if the virus gets on an environmental surface, such as a doorknob, that is then touched by other people. Direct and indirect transmissions of virus usually occur when people touch an infectious secretion and then rub their eyes or nose. RSV can survive on hard surfaces such as tables and crib rails for many hours. RSV typically lives on soft surfaces such as tissues and hands for shorter amounts of time.



Frequent handwashing and wiping of hard surfaces with soap and water or disinfectant may help stop infection and spread of RSV. Also, persons with RSV illness should not share cups or eating utensils with others.

Ideally, persons with cold-like symptoms should not interact with high-risk children. If this is not possible, these persons should cover their mouth and nose when coughing or sneezing and then wash their hands before providing any care. They should also refrain from kissing high-risk children while they have cold-like symptoms. When possible, limiting the time that high-risk children spend in child-care centers or other potentially contagious settings may help prevent infection and spread of the virus during the RSV season.

A drug called palivizumab (say "pah-lih-VIH-zu-mahb") is available to prevent severe RSV illness in certain infants and children who are at high risk. The drug can help prevent development of serious RSV disease, but it cannot help cure or treat children already suffering from serious RSV disease and it cannot prevent infection with RSV. If your child is at high risk for severe RSV disease, talk to your healthcare provider to see if palivizumab can be used as a preventive measure.

Researchers are working to develop RSV vaccines, but none is available yet.


Common Disease Taxonomy: