Merck Manual

Please confirm that you are not located inside the Russian Federation

honeypot link

Respiratory Syncytial Virus (RSV) Infection and Human Metapneumovirus Infection


Rajeev Bhatia

, MD, Phoenix Children's Hospital

Reviewed/Revised Mar 2024
Topic Resources

Respiratory syncytial virus infection and human metapneumovirus infection cause upper and sometimes lower respiratory tract infections.

  • Respiratory syncytial virus is a very common cause of respiratory infections in infants and young children.

  • Human metapneumovirus is similar to respiratory syncytial virus but is a separate virus.

  • Typical symptoms include a runny nose, fever, cough, and wheezing, and a severe infection can lead to respiratory distress.

  • The diagnosis is based on symptoms and their occurrence at expected times of year.

  • Oxygen is given as needed.

  • Nirsevimab (or palivizumab if nirsevimab is not available) is given to appropriate children to prevent respiratory syncytial virus infection.

Respiratory syncytial virus (RSV)

RSV is a very common cause of respiratory tract infection, particularly in children. Nearly all children have been infected by age 4 years, many in the first year of life. Infection does not provide complete immunity, so reinfection is common, although usually less serious. Outbreaks typically occur in winter and early spring.

Children with serious underlying disorders (such as congenital heart disease, asthma, cystic fibrosis, neuromuscular disorders, or a weakened immune system) or who were born prematurely and infants under 6 months of age are at particular risk of developing serious illness.

Older children and adults also can be infected with RSV, and older adults may develop pneumonia.

Human metapneumovirus (hMPV)

hMPV is a similar but separate virus.

hMPV occurs at the same seasonal time as RSV but does not infect as many children.

Symptoms of RSV and hMPV

RSV and hMPV cause similar symptoms. A runny nose and fever begin 3 to 5 days after infection. If the infection progresses, children also may develop a cough, wheezing, and shortness of breath.

In infants younger than 6 months old, the first symptom of RSV may be a period of not breathing (apnea).

Some children, usually young infants, develop severe respiratory distress, and a few die.

In older children and healthy adults, illness is usually mild and may manifest only as a common cold.

Diagnosis of RSV and hMPV

  • A doctor's evaluation

Doctors usually suspect RSV (and possibly hMPV) infection in young infants and children who have bronchiolitis or pneumonia during RSV season or during an outbreak. Tests are usually not done unless doctors are trying to identify an outbreak or if hospitalization is required.

Treatment of RSV and hMPV

  • Oxygen for breathing difficulty

Most children do not need to be hospitalized. Treatment at home is mainly symptom relief. For example, children may be given pain relievers and fluids to prevent dehydration Dehydration in Children Dehydration is loss of water from the body, usually caused by vomiting and/or diarrhea. Dehydration occurs when there is significant loss of body water and, to varying amounts, electrolytes... read more . Parents should closely monitor children for signs of serious breathing difficulties or dehydration.

Ribavirin, an antiviral medication, is no longer recommended except for children whose immune system is severely weakened.

Prevention of RSV and hMPV

  • Good hygiene

  • Nirsevimab (or palivizumab if nirsevimab is not available)

  • RSV vaccine for pregnant people

Practicing good hygiene is an important preventive measure. An ill child and the people in the household should wash their hands frequently. In general, the more intimate physical contact (such as hugging, snuggling, or bed sharing) that takes place with an ill child, the greater the risk of spreading the infection to other family members. Parents must balance this risk with the need to comfort an ill child.

Nirsevimab and palivizumab are two medications that contain antibodies against RSV. These medications are available in the United States for the prevention of RSV in infants and young children. Nirsevimab is the preferred medication, but it may not be available to some infants because of supply limitations. If it is not available, certain infants and children should receive palivizumab. Nirsevimab is not needed for most infants if their mother was given an RSV vaccine during pregnancy.

Nirsevimab is recommended for the following children:

  • All infants younger than 8 months of age who are either born during or who are entering their first RSV season (typically from October through the end of March in most of the continental United States)

  • Children 8 to 19 months of age who are at higher risk of becoming very sick if they get an RSV infection and who are entering their second RSV season

Nirsevimab should be given shortly before the start of the RSV season. Infants who did not receive an injection at the start of the season may be given one at any time during the season.

Nirsevimab may be given before a newborn leaves the hospital. It can be given at the same time as other routine childhood vaccines.

Palivizumab is given only if nirsevimab is not available. This medication is given as a series of injections over the course of RSV season.

Two vaccines to prevent RSV are available for older adults. In August 2023, one of these vaccines was approved for use in pregnant people at 32 to 36 weeks gestation. Giving the vaccine during pregnancy helps protect the newborn from RSV for about 6 months after birth because protective antibodies transfer from mother to fetus through the placenta. These vaccines are not yet approved for children.

There is no vaccine to prevent hMPV infection at the present time.

Drugs Mentioned In This Article

Generic Name Select Brand Names
quiz link

Test your knowledge

Take a Quiz!