RV infection of 6 day-old mice, but not mature mice, induces type 2 airway inflammation, mucous metaplasia and airways hyperresponsiveness (8) which is associated with expansion of IL-13-producing type 2 innate lymphoid cells (ILC2s) and dependent on the innate cytokines IL-25, IL-33 and TSLP (9, 10). This evidence concerns the gene IL33 and airway hyperresponsiveness.