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Respiratory Syncytial Virus (RSV)

RSV is a major cause of lower respiratory infections in young children and the elderly. In the United States, nearly all children become infected with RSV by age 2, with 75,000 to 125,000 of them hospitalized each year. Globally, RSV affects an estimated 64 million people and causes 160,000 deaths each year.​

Quick Facts

  • RSV typically causes cold-like symptoms such as a runny nose, cough, and congestion. Fevers are common. The infection can progress to the lower respiratory tract to cause more severe illness such as bronchiolitis (inflammation of the small airways in the lung) or pneumonia in otherwise healthy infants and young children.
  • RSV is highly contagious through close contact with infected people, and it can live on toys and other surfaces for several hours.
  • Most children will have an RSV infection by the time they are 2 years old, and most will get better on their own within 8 to 15 days.
  • Every year, 75,000 to 125,000 children in the United States are admitted to the hospital for RSV infections.
  • For most children, fluids are the best treatment. Bronchodilators, medicines prescribed to help reduce airway resistance, may ease breathing in some cases. Antibiotics do not work against RSV, but a healthcare provider may prescribe them for complications that develop because of RSV.
  • Although deaths are relatively rare, RSV can be life-threatening for immune-compromised people, including premature infants, young children with heart and lung problems, and the elderly.
  • Researchers are working toward a vaccine, but none currently exists.


Like influenza (flu) and some forms of the common cold, RSV is a respiratory virus that can cause lung infections. It’s often a routine childhood illness that runs its course without requiring a doctor’s attention, but it’s also the most common cause of bronchiolitis (inflammation of the small airways in the lung) and pneumonia in children less than 1 year of age.

RSV exists all over the world, but it’s active at different times of the year depending on geographical climate. Temperate regions, including most of the United States, experience RSV season during the late fall, winter, and early spring months. Tropical regions see peaks in RSV infections during the rainy season.


RSV is very contagious. It is transmitted through direct contact with nasal droplets from a person who is infected. RSV also can stay on environmental surfaces, such as doorknobs, toys, and hands, for several hours. This means it can easily be spread in school classrooms and daycare centers and brought home to other children who live there. The time between when a person is infected and when they have symptoms is about four to six days.

Because RSV does not give protection from future infections, people can get RSV many times—even during a single season. The first infection is usually the most severe. After that, any infections generally have milder symptoms.


Most children have had RSV by the time they are 2 years old, but many parents might not even realize it. That’s because RSV symptoms are very much like the symptoms of a mild-to-severe cold: runny nose, cough, mild fever, and sore throat. Infants with RSV also might have less appetite than usual and be tired or fussy. Sometimes, because congestion is heavy, infants can’t feed very well, and they may become dehydrated (have a lower than normal amount of fluids in the body). Most people will have symptoms about four to six days after being exposed to the virus.

However, RSV can be particularly dangerous in premature infants and in children with congenital heart disease or chronic lung disease, because the infection can develop into life-threatening pneumonia. It can also be dangerous for the elderly and people with compromised immune systems.

Most people with RSV cold-like symptoms do not necessarily need to visit a healthcare provider. But if you or your child have any of the following symptoms, you should call your healthcare provider immediately:

  • Trouble breathing
  • Rapid breathing
  • Episodes of sleep apnea (when breathing stops for a short time)
  • Wheezing that can be heard


Most people with RSV will simply have a runny nose and a cough and don't need to visit a healthcare provider. The virus generally runs its course with the help of home treatments. In fact, in healthy children, it’s often not necessary to find out whether they have RSV or the common cold because the treatment is the same.

But in certain cases—premature infants, children with heart and lung problems, the elderly, and people with weakened immune systems—to treat RSV properly, a healthcare provider may need to diagnose the illness. Generally, a healthcare provider can use a nasal swab or nasal wash to diagnose RSV. Sometimes, they use a chest X-ray or oxygen saturation test to check for lung congestion.


To treat RSV is to treat its symptoms. Drinking electrolyte-replacing fluids—not sugary sodas or sports drinks—regularly will prevent dehydration (abnormal loss of body fluids). Acetaminophen (Tylenol, for example) will help to reduce fever and relieve headache. Note that children with viral illnesses such as RSV should never take aspirin. In these cases, aspirin can lead to the potentially fatal Reye’s syndrome.

You should encourage children in your care to blow their noses, and you can use a bulb syringe in infants to suction nasal passages clear of mucus. Plenty of rest will help keep children comfortable until they get beter. Good handwashing can prevent spread the virus.

In more severe cases, people with RSV might need treatment to help them breathe. Some healthcare providers may prescribe a medicine called a bronchodilator to help open airways (tubes that move air from the mouth and nose into the lungs).


Researchers have been working toward an RSV vaccine since the 1950s, but no vaccine is yet licensed for use. The best way to prevent RSV is good hygiene and infection-control practices, such as washing your hands frequently with soap and water and avoiding sharing food, cups, or utensils with infected people. Using hand disinfectants will also kill the virus.

Healthcare providers may give infants at high risk for serious RSV infection or complications Synagis (palivizumab). Healthcare providers give such infants Synagis in monthly injections during the entire RSV season, because each injection gives protection for only 30 days.

NIAID Research Role

NIAID conducts and supports basic research on RSV to improve our understanding of the virus and how it causes disease, as well as factors in animals and humans that affect susceptibility to RSV infection. Scientists in NIAID labs and in universities and medical research centers across the United States work together to translate this knowledge into new, safe, and effective ways to treat and prevent RSV.

lung tissue from mice infected with pneumonia
Microscopic view of lung tissue from mice infected with pneumonia virus of mice, or PVM, a disease similar to human RSV. The tissue shows profound inflammation and an abnormal amount of fluid (in pink) collecting in the airspaces.
Credit: NIAID


For more than 50 years, NIAID’s commitment to RSV research has been unparalleled. NIAID researchers were the first to identify and characterize RSV and have provided fundamental knowledge that improves our understanding, treatment, and prevention of RSV disease.

NIAID basic research has led to the only preventive treatment currently available for RSV and given us new techniques to manipulate the virus that have brought us closer to a safe and effective vaccine.

Therapeutic Research

NIAID funds several research activities to evaluate potential new therapies for RSV. For example, one study supported in part by NIAID unveiled a possible role of the anti-influenza drug oseltamivir in treating RSV infection. The study, published in the March 2007 issue of the Journal of Immunology, found that the drug decreased RSV-induced weight loss and inhibited RSV clearance in mice, suggesting that it may be effective in moderating RSV symptoms in humans.

Scientists in the Laboratory of Allergic Diseases have developed a mouse model of a disease similar to human RSV, called pneumonia virus of mice (PVM). Studying PVM, researchers have discovered that inflammation is an important part of severe RSV disease, which suggests that using antivirals together with anti-inflammatory therapies to treat severe RSV may ease discomfort and help patients recover more quickly.

Prevention Research

Scientists in the Laboratory of Infectious Diseases (LID) were instrumental in developing palivizumab (brand name Synagis), which is currently the only preventive medicine available for RSV. LID researchers are currently working with industry on the development of candidate nasal-spray RSV vaccines. A nasal spray not only provides direct stimulation of local immunity in the nose, sinuses, throat, and lungs, it also promises to make administering the vaccine easier and less painful than using a needle.

Additionally, NIAID supports research to develop a vaccine that would help provide protection from RSV and human parainfluenza virus types 1 and 3, which also are major causes of respiratory disease in infants and young children. Researchers plan to evaluate several versions of this vaccine for immunogenicity (the ability to provoke an immune response) and advance the most promising candidates into studies of safety and effectiveness in non-human primates. ​

Featured Research

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Last Updated December 02, 2008