In the non-allergic mechanism of type 2 cytokine production, particularly in bronchial asthma, chronic airway epithelial activation in relation to environmental factors (e.g., pollutants, irritants), viral infections, or fungal exposure induces epithelial production of IL-25, IL-33, and thymic stromal lymphopoietin (TSLP). Here, TSLP is linked to viral infectious disease.