The present invention provides an agent selected from (a) an agent that increases endogeneous interferon beta (IFN-β) expression in the lung; or (b) a polynucleotide which is capable of expressing such an agent for use in the treatment of rhinovirus-induced exacerbation of a respiratory disease selected from asthma and chronic obstructive pulmonary disease (COPD), wherein said treatment is by airway delivery of said agent.