[Viral infections and asthma].

Rhinovirus, parainfluenza, influenza, adenovirus and respiratory syncytial virus respiratory tract infections are frequent causes of asthmatic exacerbations, especially in children. All these viru3es can induce bronchial inflammation which, by adding to the allergic inflammation specific to asthma, can worsen the obstruction and bronchial hyperreactivity of asthmatic patients. Respiratory viral infections can also amplify the bronchial allergic reaction induced by inhalation of an allergen and facilitate the development of asthma or an atopic state. Some viruses can induce the synthesis of specific IgE and an immunological response favouring the TH2 lymphocyte phenotype, promoting allergy. Asthma and atopy predispose to viral infections of the affected organ, possibly via local allergic inflammation (expression of ICAM1, desquamation of the mucosa, mucostasis, etc.) and/or anti-inflammatory effects of histamine.