Viral respiratory tract infections are a common aetiology of respiratory illness in children. This is especially true for patients with chronic lung disease such as asthma or cystic fibrosis (CF). They are also
a frequent cause of morbidity and hospitalisation in young children. Respiratory viral infections are thought to be associated with an increased risk of asthma. This stems from the high rate of asthma in children where there has been a history of severe viral lower
respiratory tract infections during infancy. Although respiratory syncytial virus has been traditionally implicated, it is becoming clear that rhinovirus is more important, especially rhinovirus type C. Although it is clear that children who wheeze with respiratory viruses during infancy may go on to develop asthma, many outgrow the problem. However, whether
symptomatic viral infections of the lower respiratory tract are causal in the development of asthma, or simply a predisposition, still remains controversial. The role of viral respiratory exacerbations in chronic
lung disease, especially CF, should also not be forgotten. Viruses are important contributors to deterioration in lung function, morbidity and chronic respiratory symptoms. Therefore, annual influenza
vaccination is recommended in these patients.