Rhinovirus-Induced Exacerbations of Asthma and COPD

Hershenson, Marc B.

What is the evidence for viral-induced exacerbations of asthma and COPD, and why was the role of viral infection ignored for so long? It was once thought that rhinovirus and other cold viruses did not infect the lower airway. Before the advent of polymerase chain reaction (PCR), viruses were rarely cultured from the bronchoalveolar secretions of immunocompetent individuals, even after experimental infection [1] . Early studies showed that replication of human rhinovirus (RV), the most prevalent respiratory virus, was temperature restricted, with optimal growth below body temperature, at 33 ∘ -35 ∘ C [2] [3] [4] . Exacerbations of chronic airways disease following upper respiratory tract infections were explained by theories linking nasal (upper respiratory tract) and bronchial (lower respiratory tract) disease. The most common explanation was that nasal blockage and mouth breathing lead to inspiration of cold, dry, and unfiltered air, triggering an asthma attack. However, other workers in the field blamed a nasal-bronchial reflex mechanism involving trigeminal and vagal nerves (first proposed in 1919). [5] [6] [7] [8] .