Infantile Viral Illnesses

Viruses are the predominant cause of lower respiratory tract illness in infants and a major cause of hospitalization in this vulnerable population. This chapter will review the common respiratory viral agents in infants and young children, including epidemiology and clinical and radiographic features. The role of the laboratory in diagnosis is emphasized with respect to rapid diagnostic techniques and histopathologic features in tissue sections. A brief summary of each of the major infantile respiratory viruses is provided, including respiratory syncytial virus, parainfluenza virus, adenovirus, and influenza virus, as well as the more recently detected and increasingly significant lower respiratory tract viruses, such as human metapneumovirus, coronavirus, rhinovirus, and bocavirus. Congenital and neonatal forms of viral pneumonia, such as cytomegalovirus, herpes simplex virus, and measles virus, are also discussed. Postinfectious complications of viral bronchiolitis are included in this chapter due to the significant persistent morbidity during infancy in many patients.