Introduction

Acute infections of the respiratory tract are the commonest illnesses of childhood. In Britain, respiratory infections are the most common reason for a child to be taken to a doctor, accounting for a third of all consultations between general practitioners and children. They are also the most frequent cause of acute hospital admission in childhood and account for 8–18% of acute paediatric admissions.

Most respiratory infections affect only the nose, ears and throat (the upper respiratory tract), causing a minor, self-limiting illness. But in 5–20% of infections, the lower respiratory tract is involved, often leading to more serious illness. Although the mortality from respiratory infections in children from developed countries continues to fall steadily, deaths do still occur, particularly in infants. For example, there were 204 deaths from acute respiratory infection in children in England and Wales in 1992: 63% of these were in infants less than 1 year old. By contrast, in developing countries, acute respiratory infections remain one of the commonest causes of death in children: it is estimated that, worldwide, four million children die of acute respiratory infections every year.

Children are not miniature adults. The patterns of respiratory infections in children, and the pathogens causing these infections, differ markedly from those in adults. For example, the commonest serious respiratory infection in infancy is acute viral bronchiolitis caused by the respiratory syncytial virus (RSV), a disease not seen in immunocompetent adults: the bacteria that cause life-threatening pneumonia in newborn infants are harmless bowel commensals in adults, such as group B beta-haemolytic streptococci and Escherichia coli: viral infection of the larynx and trachea is a minor illness in adults but can lead to fatal upper airway obstruction in children.