[Epidemiology of acute upper and lower respiratory tract infections in children].

More than 200 antigenically distinct viruses have been documented as causes of sporadic or epidemic respiratory infections in infants and children. The lung itself is rarely sampled directly, and sputum representing lower-airway secretions can rarely be obtained from children. In addition culture of secretions from upper respiratory tract is not useful since the normal flora includes the bacteria commonly responsible for pneumonia.