They found that the most significantly enriched pathways in ileum were the metabolic-related pathways, such as phosphoridylinositol signaling, axon guidance, and the PPAR signaling pathway, while in lung, the most significantly enriched pathways included antigen processing and presentation, T cell receptor signaling, and primary immunodeficiency, thus, indicating that the response of different tissues to viral infection was quite different. Here, PPARA is linked to viral infectious disease.