Respiratory syncytial virus (rsv) and human metapneumovirus infections

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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 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.