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 Cough in Children: A Merck Manual of Patient Symptoms podcast
Respiratory syncytial virus (RSV) and human metapneumovirus (hMPV) 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 readily available. Treatment is supportive.
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 yr. Outbreaks occur annually in winter or early spring. 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 > 100,000 hospitalizations annually in the US.
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
The most recognizable clinical syndromes are bronchiolitis (see Respiratory Disorders in Neonates, Infants, and Young Children: Bronchiolitis) and pneumonia. These illnesses typically begin with upper respiratory symptoms and fever, then progress over several days to dyspnea, cough, and wheezing. Apnea may be the initial symptom of RSV in infants < 6 mo. In healthy adults and older children, illness is usually mild and may be inapparent or manifested only as an afebrile common cold. However, patients who are elderly or immunocompromised or who have underlying cardiopulmonary disorders may develop severe disease.
RSV and hMPV illness appear to be similar.
Diagnosis
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 are available for use in children; nasal washings or swabs are used. These tests are insensitive in adults.
Treatment
Treatment of RSV and hMPV infections is supportive and includes supplemental O2 and hydration as needed (see Respiratory Disorders in Neonates, Infants, and Young Children: Bronchiolitis).
Corticosteroids and bronchodilators are not generally helpful.
Antibiotics are reserved for patients with fever and evidence of pneumonia on chest x-ray (ie, who may have a bacterial superinfection).
Palivizumab (monoclonal antibody to RSV) is not effective for treatment.
Inhaled ribavirin, an antiviral drug with activity against RSV, has little or no efficacy, is potentially toxic to health care practitioners, and is no longer recommended except for infection in severely immunocompromised patients.
Prevention
Contact precautions (eg, hand washing, gloves, isolation) are important, particularly in hospitals.
Passive prophylaxis with palivizumab decreases the frequency of hospitalization in high-risk infants. It is cost-effective only for infants at high risk of hospitalization (ie, those < 2 yr with hemodynamically significant congenital heart disease or chronic lung disease requiring medical treatment in the preceding 6 mo, those who were born at < 29 wk gestation and are < 1 yr old at the start of RSV season, and those who were born at 29 to 32 wk gestation and are < 6 mo at the start of the season). The dose 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-mo intervals for the duration of the RSV season (usually a total of 5 doses).
Last full review/revision October 2009 by Ronald B. Turner, MD
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