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 chapter covers viral infections that are typically acquired during childhood (although many 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.
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:
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.
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).
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
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 policy statement about palivizumab prophylaxis for infants and young children who are at increased risk of hospitalization for RSV.)
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.
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