Definition. Respiratory syncytial virus (RSV) is a large, enveloped RNA paramyxovirus. Two major strains (groups A and B) have been identified and often circulate concurrently.
Incidence. Almost all children are infected at least once by 2 years of age. Humans are the only source of infection. Initial infection occurs most commonly during the child's first year. Reinfection throughout life is common. In the United States, RSV usually occurs in annual epidemics during winter and early spring (predominantly November through March). It is a common cause of nosocomial infection. It can survive up to 6 h on nonporous surfaces. Most cases of bronchiolitis in infants are caused by RSV.
Pathophysiology. The disease is limited to the respiratory tract. The inoculation of the virus occurs in the upper respiratory tract where it spreads to the lower tract by cell-to-cell transfer. In infants the disease usually involves the lower respiratory tract and manifests itself as bronchiolitis or pneumonia.
Risk factors. Risk factors include premature infants, infants born with lung disease, infants <2 years of age with heart disease, infants with a birthweight <2500 g, infants with school-age siblings, infants who attend daycare, family history of asthma, regular exposure to secondhand smoke or air pollution, multiple birth babies, peak RSV season (fall to end of spring), being male, <1 month or no breast-feeding and others sharing the bedroom with the infant. High altitude increases the risk of RSV hospitalization. Risk factors for more severe or fatal RSV disease include a premature infant, an infant with cyanotic or complicated congenital heart disease (CHD) especially those that cause pulmonary hypertension, an infant with pulmonary disease, especially bronchopulmonary dysplasia (chronic lung disease [CLD]), those infants with immunodeficiency with lymphopenia, or therapy causing immunosuppression. Asthma is associated with an increased susceptibility to severe RSV disease.
Clinical presentation. RSV usually begins in the nasopharynx with coryza and congestion. During the first 2–5 days, it may progress to the lower respiratory tract with development of cough, dyspnea, and wheezing. RSV is the most important cause of bronchiolitis and pneumonia. Lethargy, irritability, and poor feeding often accompanied by apneic episodes may be the presenting manifestations in young infants. Most previously healthy infants infected with RSV do not require hospitalization. Characteristics that increase the risk of severe or fatal RSV infection are preterm birth without or especially with CLD of prematurity; hemodynamically significant CHD especially if associated with cyanosis or pulmonary hypertension; and T-cell immunodeficiency disease or therapy causing immunosuppression. RSV infection predisposes to reactive airway disease and recurrent wheezing during the first decade of life.
Enzyme-linked immunoabsorbent assay (ELISA) and direct fluorescent antibody tests (DFA) have sensitivity (in comparison with culture) in the range of 80–90%. These rapid tests detect RSV antigen in epithelial cells obtained by nasopharyngeal washings.
Chest radiograph usually reveals infiltrates or hyperinflation.
Blood gas analysis may show hypoxemia and occasionally hypercarbia. Development of hypercarbia is an ominous sign of impending respiratory failure.
Management. Isolation precautions for all infectious diseases, including maternal and neonatal precautions, breast-feeding, and visiting issues, can be found in Appendix F.
Passive. Palivizumab (Synagis) provides passive immunity. It is a humanized RSV monoclonal antibody and administered intramuscularly (15 mg/kg) monthly during RSV season. It is well tolerated with infrequent or minimal side effects. According to the American Academy of Pediatrics guidelines, palivizumab should be considered for:
Infants and children <2 years with CLD who have required medical therapy (supplemental oxygen, ...
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