Viral infections are sensed by innate immunity through pattern recognition receptors (PRRs), including Toll-like receptor 3 (TLR3), retinoic acid-inducible protein I and melanoma differentiation-associated gene 5.89–92 Zhu, et al. in 2018 reported low expression of IFN-α and IFN-β in the macrophages of airway epithelium and subepithelium in asthmatic patients. Here, TLR3 is linked to viral infectious disease.