Considering that the pattern of T-helper 2 (Th2) cytokines observed in respiratory secretions during hMPV LRTI may sometimes resemble that of individuals with asthma (including eosinophilic inflammation, higher interleukin-4 [IL-4] and IL-5 levels in mouse models [16], and induction of thymic stromal lymphopoietin in human airway cells [17, 18]) we speculated that a history of asthmatic predisposition could specifically modify severity of hMPV disease in children. This evidence concerns the gene IL4 and asthma.