Pneumonia and OtherRespiratory Infections

eEPIDEMIOLOGY Pneumonia is a leading killer of children, causing an estimated 1.9 million deaths worldwide in children under the age of 5 years (Fig. 1).1,2 The true mortality caused by pneumonia probably is underestimated, because most deaths in developing na-tions occur at home without a true medical diagnosis. Ninety percent of the deaths are thought to occur in the developing world, with 50 % of these occurring in Africa.3 The incidence of pneumonia in North America and Europe is approximately 36 per 1000 per year.4,5 Thus, although mortality is low, pneumonia causes significant mor-bidity even in developed countries. DEFINITION Pneumonia can be defined solely by clinical features6 or with the addition of radiologic findings. In part because of the considerable overlap between the diagnosis of bron-chiolitis and pneumonia in young children,4 ‘‘lower respiratory illness’ ’ is a frequently used alternative term. Lower respiratory illness has been defined as fever, acute respi-ratory symptoms, and radiologic evidence of parenchymal infiltrates; the World Healt