Introduction

Viruses are the most common cause of lower respiratory tract disease in infants and young children and are a major public health problem in this age group. The novel variant of coronavirus that is associated with the worldwide outbreak of severe acute respiratory syndrome and human metapneumovirus, a recently identified new respiratory pathogen, have stressed the continuing importance of viral respiratory infections over the whole age spectrum.

Costs attributable to viral lower respiratory tract infections in both outpatient and inpatient settings are an important burden on national healthcare budgets.1 Each year approximately 3% of all children less than 1 year of age need to be admitted to hospital with moderate or severe viral lower respiratory tract infection.2 This review gives an update of viral lower respiratory tract infection in infants and young children, with special emphasis on treatment and prevention.

Sources and selection criteria

We gathered information from our own experience and by reading relevant literature on viral respiratory infections in infants and children obtained by searching Medline and the Cochrane database. Much literature is available on the topic, so we based our review on well designed major observational studies, controlled trials, and systematic reviews. We consulted the websites of the World Health Organization and the Centers for Disease Control for the most recent information on severe acute respiratory syndrome.

Epidemiology

A great variety of viruses can cause lower respiratory tract disease in children—for example, respiratory syncytial virus, influenza viruses, parainfluenza viruses, rhinovirus, adenovirus, and the recently identified human metapneumovirus.3,^w1,w2 Although most respiratory viral infections occur throughout the year, seasonal variation (in a worldwide comparable pattern) is obvious for certain viruses, such as respiratory syncytial virus and influenza virus (figure).