The Role of Viral Respiratory Infections in Asthma and Asthma Exacerbations

Busse, William W.; Lemanske, Robert F.; Gern, James E.

Viral respiratory tract infections are frequent and usually self-limited illnesses. For patients at risk for asthma, or with existing asthma, viral respiratory tract infections can have a profound effect on the expression of disease or loss of control. New evidence has shown that wheezing episodes early in life with the common cold virus, human rhinovirus, is a major risk factor for the later diagnosis of asthma at age six years. For those with existing asthma, exacerbations are a major cause of morbidity, need for acute care and, rarely, death. Viral respiratory tract infections, most frequently with rhinovirus, are the predominant microorganisms associated with asthma exacerbations. Evidence is also emerging that deficiencies in antiviral activity and the integrity of the airway epithelial barrier may make individuals with asthma more likely to have severe viral respiratory infections of the lower airway, and thus increase the risk of exacerbation. Given the influences of respiratory viruses on many aspects of asthma, efforts to understand the mechanisms and risk factors by which these airway infections cause changes in airway pathophysiology are a first step in improved treatment.