A molecular mechanism that could explain why the common cold can bring on life-threatening asthma attacks has been revealed by researchers. Viruses that infect the airways are the most common cause of asthma attacks, accounting for 80-90 per cent of cases. The great majority of these are rhinoviruses, which are the predominant cause of the common cold. In people with respiratory diseases such as asthma, they can trigger severe attacks, sometimes leading to hospitalization.