Merck Manual

Please confirm that you are a health care professional

honeypot link

Respiratory Syncytial Virus (RSV) and Human Metapneumovirus Infections


Brenda L. Tesini

, MD, University of Rochester School of Medicine and Dentistry

Last full review/revision Jun 2021| Content last modified Jun 2021
Click here for Patient Education

Respiratory syncytial virus and human metapneumovirus infections cause seasonal lower respiratory tract disease, particularly in infants and young children. Disease may be asymptomatic, mild, or severe, including bronchiolitis and pneumonia. Although diagnosis is usually clinical, laboratory diagnosis is available. Treatment is supportive.

Most viruses that infect humans can affect both adults and children and are discussed elsewhere in THE MANUAL. Viruses with specific effects on neonates are discussed in Infections in Neonates. This topic covers a viral infection that is typically acquired during childhood (although it may also affect adults).

Respiratory syncytial virus (RSV) is an RNA virus, classified as a pneumovirus. Subgroups A and B have been identified. RSV is ubiquitous; almost all children are infected by age 4 years. Outbreaks occur annually in winter or early spring in temperate climates. Because the immune response to RSV does not protect against reinfection, the attack rate is about 40% for all exposed people. However, antibody to RSV decreases illness severity. RSV is the most common cause of lower respiratory tract illness in young infants and is responsible for > 50,000 hospitalizations annually in the US in children under the age of 5 years.

Human metapneumovirus (hMPV) is a similar but separate virus. The seasonal epidemiology of hMPV appears to be similar to that of RSV, but the incidence of infection and illness appears to be substantially lower.

Symptoms and Signs

RSV and hMPV illness manifest similarly. The most recognizable clinical syndromes are bronchiolitis and pneumonia. These illnesses typically begin with upper respiratory symptoms and fever, then progress over several days to dyspnea, cough, wheezing, and/or crackles on chest auscultation. Apnea may be the initial symptom of RSV in infants < 6 months. In healthy adults and older children, illness is usually mild and may be inapparent or manifested only as an afebrile common cold. However, severe disease may develop in the following:

  • Patients who are < 6 months, elderly, or immunocompromised

  • Patients who have underlying cardiopulmonary or neuromuscular disorders


  • Clinical evaluation

  • Sometimes rapid antigen tests, reverse-transcription–polymerase chain reaction (RT-PCR), or viral culture—all done on nasal washings or swabs

RSV (and possibly hMPV) infection is suspected in infants and young children with bronchiolitis or pneumonia during RSV season. Because antiviral treatment is not typically recommended, a specific laboratory diagnosis is unnecessary for patient management. However, a laboratory diagnosis may facilitate hospital infection control by allowing segregation of children infected with the same virus. Rapid antigen tests with high sensitivities for RSV and other respiratory viruses are available for use in children; nasal washings or swabs are used. These tests are less sensitive in adults. Molecular diagnostic assays such as RT-PCR have improved sensitivity and are generally available as single or multiplex assays.


  • Supportive care

Treatment of RSV and hMPV infections is supportive and includes supplemental oxygen and hydration as needed (see treatment of bronchiolitis).

Corticosteroids and bronchodilators are generally not helpful and are currently not recommended.

Antibiotics are reserved for patients with fever, evidence of pneumonia on chest x-ray, and clinical suspicion of a bacterial coinfection.

Palivizumab (monoclonal antibody to RSV) is not effective for treatment.

Inhaled ribavirin, an antiviral drug with activity against RSV, has marginal efficacy, is potentially toxic to health care practitioners, and is no longer recommended except for infection in severely immunocompromised patients. Numerous drugs targeting viral fusion, entry, and replication for adults and infants are currently in development and in clinical trials (1).

Treatment reference


Contact precautions (eg, hand washing, gloves, isolation) are important, particularly in hospitals.

Passive prophylaxis with palivizumab decreases the frequency of hospitalization for RSV in high-risk infants. It is cost-effective only for infants at high risk of hospitalization, including those who

  • Are < 1 year with hemodynamically significant congenital heart disease

  • Are < 1 year with chronic lung disease of prematurity (gestational age < 32 weeks and 0 days with the need for oxygen therapy for at least 28 days after birth)

  • Are born at < 29 weeks gestation and are < 1 year old at the start of RSV season

  • Have chronic lung disease of prematurity in the 2nd year of life and have received treatment (chronic corticosteroid or diuretic treatment or continued need for oxygen therapy) within 6 months of RSV season

Prophylaxis may also be considered for

  • Infants in the 1st year of life who have anatomic pulmonary abnormalities that impair the ability to effectively clear the upper airways

  • Infants who have neuromuscular disorders

  • Children < 24 months who have profound immunocompromise

The dose of palivizumab is 15 mg/kg IM. The first dose is given just before the usual onset of the RSV season (early November in North America). Subsequent doses are given at 1-month intervals for the duration of the RSV season (usually a total of 5 doses). (See also the American Academy of Pediatrics' updated 2014 policy statement about palivizumab prophylaxis for infants and young children who are at increased risk of hospitalization for RSV.)

Several maternal, pediatric, and adult RSV vaccines are in development in clinical trials (1).

Prevention reference

Key Points

  • Respiratory syncytial virus (RSV) and human metapneumovirus usually cause a syndrome of bronchiolitis, but pneumonia may occur.

  • Diagnosis is usually clinical, but testing, including rapid antigen tests and molecular assays (eg, reverse-transcription–polymerase chain reaction), is available.

  • Give supportive treatment; corticosteroids, bronchodilators, and palivizumab are not recommended.

  • Inhaled ribavirin may be useful for RSV but only in severely immunocompromised patients.

  • Passive prophylaxis with palivizumab just before and during RSV season decreases the frequency of hospitalization in specific high-risk infants.

More Information

The following is an English-language resource that may be useful. Please note that THE MANUAL is not responsible for the content of this resource.

Drugs Mentioned In This Article

Drug Name Select Trade
Click here for Patient Education
NOTE: This is the Professional Version. CONSUMERS: Click here for the Consumer Version
Professionals also read

Test your knowledge

Neonatal Herpes Simplex Virus (HSV) Infection
Neonatal herpes simplex virus (HSV) infection has a high morbidity and mortality rate. The usual presenting symptom in neonates is a vesicular eruption that appears between the 1st and 3rd week of life. There are several ways in which this disease is transmitted to the neonate. Of these modes of transmission, which of the following is the most common? 
Download the Manuals App iOS ANDROID
Download the Manuals App iOS ANDROID
Download the Manuals App iOS ANDROID

Also of Interest