The major morbidity, mortality and health care costs associated with asthma are related to exacerbations. In order to reduce this massive healthcare burden, the prevention and treatment of exacerbations needs to be a greater focus for research. The following review is based on the presentations made at the first International Congress on Exacerbations of Airway Disease and summarises the current state of research on acute exacerbations of asthma.

The lack of a universally accepted definition for an exacerbation of asthma creates difficulties for interpretation of clinical research and trial results. Recently, an ERS/ATS task force addressed this, and to encourage uniformity defined moderate and severe exacerbations based on the actions of the patient and physician rather than symptoms (unpublished information). These definitions are a step forward for trial design and interpretation but it is acknowledged that no single definition will fit all clinical research needs.

EXACERBATION AETIOLOGY

Approximately 80% of asthma exacerbations are associated with respiratory viral infections, and rhinoviruses (RV) are responsible for about two-thirds of these.1 Despite the importance of viral infections, a combination of interacting factors is likely to be involved. A synergistic interaction between allergen sensitisation, allergen exposure and virus infection has been detected in adult patients with asthma during acute exacerbations. Sensitised, exposed and infected patients had a significantly increased risk of admission for exacerbations.2 An even greater interaction exists in children.3

The role of RV in exacerbations has been investigated in a human experimental model in patients with mild asthma. During acute infection, patients with asthma had increased lower respiratory tract symptoms, falls in lung function and increases in bronchial hyperresponsiveness compared with those without asthma. Virus load correlated strongly with asthma symptoms and hyperresponsiveness, implicating severity of infection as the main determinant of exacerbation severity (data submitted for publication). Interferon β production …